<p align="center">
<a href="https://goa.design/docs/2-goa-ai/#gh-light-mode-only">
<picture>
<source media="(max-width: 600px)" srcset="docs/img/goa-ai-banner-mobile.png">
<img alt="Goa-AI: one Go design generates typed agent tools, MCP clients and servers, and HTTP and gRPC APIs." src="docs/img/goa-ai-banner.png" width="960">
</picture>
</a>
<a href="https://goa.design/docs/2-goa-ai/#gh-dark-mode-only">
<picture>
<source media="(max-width: 600px)" srcset="docs/img/goa-ai-banner-mobile-dark.png">
<img alt="Goa-AI: one Go design generates typed agent tools, MCP clients and servers, and HTTP and gRPC APIs." src="docs/img/goa-ai-banner-dark.png" width="960">
</picture>
</a>
</p>
<p align="center">
<a href="https://github.com/goadesign/goa-ai/releases/latest"><img alt="Release" src="https://img.shields.io/github/v/release/goadesign/goa-ai"></a>
<a href="https://github.com/goadesign/goa-ai/actions/workflows/ci.yml"><img alt="CI" src="https://img.shields.io/github/actions/workflow/status/goadesign/goa-ai/ci.yml?branch=main"></a>
<a href="https://pkg.go.dev/goa.design/goa-ai"><img alt="Go reference" src="https://pkg.go.dev/badge/goa.design/goa-ai.svg"></a>
<a href="LICENSE"><img alt="MIT license" src="https://img.shields.io/badge/license-MIT-blue.svg"></a>
</p>
# Goa-AI: agents, MCP, and tool registries in Go
**Design your capabilities once. Generate the contracts that connect your services, AI agents, and MCP clients.**
Goa-AI extends [Goa](https://goa.design) with AI agents, the Model Context Protocol
(MCP), and distributed tool registries. Write a design in Go; generate typed
clients, servers, model schemas, validation, and runtime wiring. Implement your
application's behavior in ordinary Go.
Design tools can read the generated [per-agent schema catalog](docs/dsl.md#agent-specs-specs),
including consumer-bound, lookup, and text-only input contracts, without running
application bindings.
For engineers, this means fewer contracts to maintain and compiler feedback when
they change. For coding agents, it means explicit types, generated validation,
and an application-specific guide to the code they need to implement.
**[Run the quickstart](#quick-start)** · **[Explore the guides](https://goa.design/docs/2-goa-ai/)** · **[Upgrade to v0.89.0](docs/releases/v0.89.0.md#required-upgrade-actions)**
## Choose what you want to build
| Your goal | Start here |
| --- | --- |
| **An AI agent** that calls typed tools, returns structured answers, and can pause for human input | [Agent quickstart](quickstart/README.md) |
| **Composable prompts and scoped overrides** with compile-time AST validation, sub-prompt composition, and OpenTelemetry tracing | [Composable prompt management](docs/prompts.md) |
| **An MCP server** exposing Go service methods, resources, and prompts, or **an MCP client** consuming them | [MCP integration guide](https://goa.design/docs/2-goa-ai/mcp-integration/) |
| **A tool registry** that publishes capabilities across services and lets agents discover independently implemented Agent operations without loading provider code, or binds generated native tools to selected registrations while retaining typed codecs and child routes | [Registries and tool search](docs/tool_search.md) |
Catalog owners can [inspect active registration facts](docs/tool_search.md#inspect-active-registration-facts)
without loading tool declarations, using the saved identity, exact token and
service-or-native kind.
Low-level runtime and custom Store integrations use a required generated
[run subject](docs/run-subjects.md) to identify the actual executor. Read its
upgrade requirements before changing a deployment with saved runs.
These capabilities compose. You can also use MCP servers and clients independently
of the agent runtime.
Paged agent tools declared with `ContinueWith` publish one operation for both
the initial query and subsequent pages. Direct callers supply the declared page
arguments; agents receive temporary no-argument actions tied to the exact query.
See [pagination ownership](DESIGN.md#pagination-ownership) for the generated
input and execution contracts.
## One design, several ways to use it
A product lookup can be an HTTP endpoint, a gRPC method, an MCP tool, and a local
agent tool. The input, output, descriptions, and validation come from the same
design:
```go
package design
import (
. "goa.design/goa/v3/dsl"
. "goa.design/goa-ai/dsl"
)
var Lookup = Type("Lookup", func() {
Field(1, "sku", String, "Product SKU", func() { MinLength(1) })
Required("sku")
Example(map[string]any{"sku": "SKU-123"})
})
var Product = Type("Product", func() {
Field(1, "name", String, "Product name")
Required("name")
})
var _ = Service("catalog", func() {
Description("Look up products for applications and shopping assistants.")
MCP("catalog", "1.0.0")
JSONRPC(func() { POST("/mcp") })
Method("lookup", func() {
Description("Retrieve a product by its SKU.")
Payload(Lookup)
Result(Product)
HTTP(func() { GET("/products/{sku}") })
GRPC(func() {})
Tool("lookup", "Look up a product by SKU")
})
Agent("shopper", "Help customers find products", func() {
Use("products", func() {
Tool("lookup", "Look up a product by SKU", func() {
BindTo("lookup")
})
})
})
})
```
Run generation using the Goa version selected by your application:
```bash
go run goa.design/goa/v3/cmd/goa gen <design-package-import-path>
```
| From this design | You get |
| --- | --- |
| Service contract | Typed Go interfaces, payloads, results, and validation |
| Agent tool | Model-facing JSON Schema, examples, codecs, and a service executor |
| Composable prompt | Validated AST, typed args struct, spec builder, and typed render helper |
| MCP tool | A typed client and HTTP server with discovery and input/output schemas |
| HTTP and gRPC methods | Clients, servers, OpenAPI, and protobuf definitions |
Change a field and regenerate these contracts together. Your implementation,
planner, authorization, and business rules remain application code. Ordinary
methods can coexist with MCP tools in the same service.
Tools can expose a focused subset of a method's inputs and results, inject
server-owned values, or return a selected Goa result view. The generator handles
the declared transforms. See [service bindings](docs/dsl.md#bindto-service-method-binding)
and [MCP composition](docs/dsl.md#mcp-server-definition).
## Quick start
With **Go 1.27.0 or newer**, run the checked-in example:
```bash
git clone https://github.com/goadesign/goa-ai.git
cd goa-ai/quickstart
go run ./cmd/orchestrator
```
It runs the real agent loop and typed completions with a deterministic planner
and an in-memory engine and store. **No model API key, Temporal, Redis, or MongoDB
is required.** You'll see:
```text
Assistant: Tool helpers.answer returned {"text":"Tokyo is the capital of Japan."}
Completion draft_task: Prepare launch checklist (Confirm the service is ready to launch.), 3 steps
```
Run its evaluation suite:
```bash
go run ./cmd/chat_quality-evals
```
The [quickstart guide](quickstart/README.md) walks through the design, generation,
service wiring, and connecting a model. For MCP, follow the
[MCP integration guide](https://goa.design/docs/2-goa-ai/mcp-integration/).
## What you can build
### Agents and typed outputs
- **Typed tools and structured answers.** Bind tools to Goa methods or custom
executors; declare `Completion(...)` for typed direct responses. Generated
codecs and schemas enforce the authored contract. Completion helpers preserve
the caller's thinking settings; see the [runtime guide](docs/runtime.md#typed-direct-completions)
for provider defaults and explicit disabled thinking.
- **Composable prompts and scoped overrides.** Declare agent system instructions
and shared prompt templates in Goa design. Templates compile with `missingkey=error`
and validate field references against typed `Args` at generation time. Compose
sub-prompts via `{{ render "<prompt_id>" . }}` and manage scoped overrides
dynamically with exact-scope reset and OpenTelemetry model span tracing.
- **Correction of invalid tool calls.** Missing fields, wrong types, and invalid
values receive specific feedback and authored examples. The runtime can ask
the model for a replacement within your recovery budget, before execution.
- **Specialist agents.** Expose agents as tools and compose real child runs with
linked progress and cancellation. Cancellation preserves completed results
and waits for required cleanup before closing the run; cleanup failures remain errors.
Child workflow IDs stay bounded for long names and repeated nesting; see the
[identifier and worker upgrade contract](docs/runtime.md#child-run-identifiers-and-worker-upgrades).
- **Human input and approvals.** Save a pending question or confirmation and
continue from the host's answer. Direct and registered operations share durable
continuation submission and completion. Hosts supply each successor workflow's
Memo explicitly; recovery preserves it and rejects changed answers or metadata.
Canceling a root question with no saved child or remote work closes its
continuation while preserving the original
suspended result. Text-only runs exclude interactive tools. Hosts can apply the
same restriction to exact direct and registered operations with `WithTextOnly(true)`.
- **Large results and images.** Bound model-visible results, continue paginated
queries, retain native image evidence, and keep rich host data outside model
requests. Saved history remains readable after tool changes; only compatible
current tools can supply another page. Outbound run-log record encoding applies
the workflow payload allowance before publication; complete records assembled
inside storage and historical reads preserve separately accepted data.
[Agent DSL](docs/dsl.md#agent-use-and-export) · [Composable prompts](docs/prompts.md) · [Runtime and composition](docs/runtime.md) · [Native images](docs/native_images.md)
### MCP clients and servers
- **MCP 2026-07-28 over HTTP.** Generate stateless servers and typed clients with
discovery, tools, structured results, and ordered text, image, audio, resource
links, and embedded resources. Consumers also support stdio; generated stdio
servers are deferred. Generated HTTP servers also accept basic `2025-11-25`
clients on the same URL, using the same configured Goa endpoints. See the
[older-client contract](docs/runtime.md#older-http-clients).
- **Runtime-defined tools.** Declare `DynamicTools()` to implement tool listing
and invocation through generated protocol types without authored static tools.
Older clients receive dynamic structured results in a matching `value` object;
modern clients receive the original JSON value.
See [runtime-defined tools](docs/dsl.md#runtime-defined-tools).
- **Resources and prompts.** Serve fixed or parameterized text/binary resources,
typed prompts, argument completion, and authenticated paginated catalogs.
- **Progress and subscriptions.** Report progress from ordinary service methods;
observe catalog changes, resource updates, and full Task state. Silent HTTP
responses use transport keepalive comments without requiring service progress.
**Regenerate MCP servers when upgrading:** a dependency-only update leaves
streaming before middleware. Follow the [required upgrade](docs/runtime.md#request-scoped-mcp-progress).
- **Additional input and durable Tasks.** Collect form input or URL consent;
preserve additional protocol members without changing declared fields;
expose existing durable jobs with creation, observation, answers, and
cancellation. The same native methods work as local and registry tools.
- **Authorization.** Compose browser OAuth, machine credentials, signed client
authentication, and enterprise identity exchange. Servers verify configured
signed tokens or use token introspection. Hosts own trusted registration,
consent, and private credential storage.
- **Apps and Skills.** Associate tools with HTML app resources and caller
visibility; publish Skill catalogs and files with manifest verification.
Reference hosts demonstrate browser isolation and content-bound approval.
[MCP declarations](docs/dsl.md#mcp-server-definition) · [Clients and authorization](docs/runtime.md#mcp-callers) · [Apps example](integration_tests/apps/README.md) · [Skills guide](docs/mcp_skills.md)
Context-limit responses are recovered by the workflow rather than accepted as
completed answers or executable tool batches. The runtime uses its existing
history policy to summarize older turns before a replacement request, preserves
live text and usage, and stops if compaction cannot shorten the input. This
uses the existing recovery-turn budget. See
[context-window recovery](docs/runtime.md#context-window-recovery).
Initial-history writes reference the already bound preparation operation; seed
reads return its original invocation without duplicating it in bounded commands.
Custom stores must follow the [preparation ownership upgrade](docs/runtime.md#preparation-ownership-upgrade).
### Registries, search, and production execution
- **Distributed tool registries.** Publish typed toolsets, discover changing
catalogs, and route calls to providers with exact contracts and renewable leases.
Providers can bound individual Registry operations independently of accepted-call
shutdown; omitted options retain existing behavior. See
[provider lifecycle](docs/runtime.md#registry-routed-provider-execution-service-side).
Regenerate application gRPC code to adopt nullable collection conversion fixes;
[converter and wire rules](DESIGN.md#registry-integration) remain separate.
Catalogs retain resource ownership; applications authorize discovery and use.
Newly committed native declarations retain an independently owned saved
representation and its exact-byte digest for local reuse; cold reads strictly
validate saved bytes. Reads still check current bytes, state and retirement.
`Service.ReadSavedCatalogToolset` reads an exact saved declaration after
retirement without reporting health or granting new execution; active catalog
reads and provider admission keep rejecting retired registrations.
Local maintenance tools can use `registry.NewCatalogReader` to inspect saved
registrations without starting workers or writing Redis data; see
[read-only catalog inspection](docs/runtime.md#read-only-catalog-inspection).
Registered imports derive distinct names for equal operations from different
owners and retain original declarations for execution and replay.
Portable bounded-result codecs accept provider result data; the runtime adds
counts and truncation before publishing results against the advertised schema.
Generated Agent declarations also retain each operation's authored timeout
recovery policy through registry transport; see the
[regeneration requirements](docs/runtime.md#agent-timeout-recovery).
- **Bind generated tools to selected services.** Keep generated tool names,
input preparation, codecs, and executors while attaching an exact owner-selected
registration. Calls and retries retain the original route and token. New pages
select today's provider after the resource owner verifies prior registrations;
saved queries and completed results remain unchanged. See
[static service bindings](docs/tool_search.md#bind-generated-service-tools).
Binding validates complete generated declarations without expanding the
consuming Agent's executable tools; separately discovered tools remain available.
When the selected declarations remain fixed, compile their complete match once
with `CompileStaticService`, then use `BindCompiledStaticService` for each
activity. The immutable value retains compact call selections, not full
catalogs or authority; current selection and admission remain caller-owned.
- **Standalone service operations.** Execute a registered service tool without
creating a session; sessionful calls retain their existing session. Direct calls
validate complete execution arguments, including retained query fields and
continuation cursors, while excluding provider-injected fields. Protocol 15
requires coordinated registry, provider, and consumer upgrades; see
[session metadata and upgrade](docs/runtime.md#session-metadata-and-upgrade).
Registry startup preserves historical declaration identities without decoding
old consumer metadata as today's executable contract, allowing saved-result
recovery before provider replacement. This does not change typed historical
resolution when removed metadata fields cannot fit the current response.
`GetToolsetSchemas` returns original descriptive fields and input/output schemas
for inspection without executable metadata or registration authority.
- **Direct Agent operations.** Start typed operations before tool publication,
using the same provider preparation and result contract as delegation.
[Revision-owned providers](docs/runtime.md#revision-owned-operation-contracts)
load and verify complete exports from the selected immutable configuration.
Providers can select literal messages or exact completed-run history with
retained privacy exclusions; see the [resolver upgrade](docs/runtime.md#provider-owned-history).
- **Load tools when needed.** Use deferred tool search for whole toolsets or
selected compiled tools, through supported OpenAI and Claude integrations.
- **Durable execution.** Retain failures and cancellation even before the first
Run is stored. Use Temporal and an application-owned durable store to
retain accepted work, host continuations, remote Task identity, and cancellation
across worker restarts. New turns preserve saved results completed by a later
run, including conversations stored as literal history. Failed calls stay in
the transcript and do not block later turns by restoring old paging state.
Saved results without bounds remain evidence and supply no next page;
completed page chains remain readable after their tool inputs change.
Obsolete unfinished queries offer no page action but do not block new turns;
current bounded results still require bounds and valid arguments.
Paged operations retain each query and page branch's declared progress labels
and result previews under the same public tool name. Regenerate callers after
upgrading to install the matching templates.
Steps that combine provider-selected calls with extra planner-created calls
retain every call and result for the next planner activity, including after
suspension. Completed tool results, accepted arguments, media, and rendered
previews remain readable through clarification resumes after their generated
result type changes or their tool is removed. Pending execution, result
materialization, confirmations, child runs, and unfinished paging still use current
generated contracts. Original provider messages and reasoning signatures stay
unchanged.
The in-memory engine supports local development.
- **Exact root worker builds.** `WithRootExecutionTarget` selects one worker
deployment and build for an accepted root request. Prepared starts, retries,
and completion repair preserve that target; child routing remains generated.
Each new answer or cancellation continuation leaves worker selection to the
engine. Temporal chooses current workers and uses their configured versioning
behavior; default pinned versioning keeps that execution on its assigned build.
Retrying an already published request preserves its original launch settings.
- **Native Temporal handlers.** Register SDK workflows and activities alongside
agent handlers, and read the exact workflow and activity queues from successful
registrations before starting workers.
- **Policies and context.** Control permitted tools, call and recovery budgets,
timing, history compression, prompt caching, and prompt overrides. Runtime
model clients preserve provider token counting without creating an inference
record or span; see [model middleware](docs/runtime.md#model-middleware).
- **Evaluation and observability.** Generate typed evaluation suites; observe
assistant text, tool progress, child runs, usage, and OpenTelemetry traces.
- **Standalone JSON codecs.** Generate typed validators and strict JSON
encoders and decoders beside ordinary Goa types, independently of agent and
MCP declarations.
[Registries and search](docs/tool_search.md) · [Production configuration](docs/runtime.md#production-configuration) · [Evaluations](docs/evals.md) · [JSON codecs](docs/json_codecs.md)
## Build with a coding agent
Install the **Goa service designer skill** in your application project
(requires Node.js and npm):
```bash
npx skills add goadesign/goa --skill goa-service-designer
```
Give your coding agent the generated `AGENTS_QUICKSTART.md`. It names **your**
agents, tools, packages, and registration functions. A useful first task:
> Add a product lookup tool backed by the catalog service. Update the Goa design,
> regenerate, implement the service method, and verify valid and invalid calls.
> Use AGENTS_QUICKSTART.md for wiring. Do not edit gen/.
`goa gen` replaces generated contracts. `goa example` creates missing application
scaffolding without overwriting existing files. Your application behavior stays
yours. See the [coding-agent workflow](https://goa.design/docs/ai-development/).
## Take it to production
Choose model adapters for OpenAI, Anthropic, Amazon Bedrock, Google Vertex AI,
or a model gateway. [Provider support](docs/runtime.md#model-clients) varies by
model and API. Optional integrations include MongoDB for memory and prompt
overrides, and Redis/Pulse for streams and registries.
Your application owns planners, service behavior, authorization, side-effect
idempotency, durable storage, and deployment. Configure the Temporal engine
**and** a durable runtime store for restart-safe execution. A trusted host
receives runtime events and decides what to expose to users.
**v0.89.0 is a breaking upgrade.** Regenerate and coordinate servers, clients,
providers, runtime workers, and storage implementations. Older MCP revisions,
registry wire versions, and suspension checkpoints are not interchangeable.
Read the [release and upgrade instructions](docs/releases/v0.89.0.md) before
replacing existing deployments; a source rollback alone cannot undo new stored
work.
When binding generated service or Agent tools, the previous-registration reader
returns the owner's exact `ResolvedToolset`, or nil without an error when the
saved registration has no matching current resource. That query offers no new
page, while its saved messages and results remain readable. A failed read or
malformed binding still stops planning. Every member of a page chain is checked
before an unavailable chain is omitted. The returned declarations let new pages
verify their saved declarations while using current input and paging rules,
including after a tool description changes. See [static tool binding](docs/tool_search.md#bind-generated-service-tools).
## Learn more
- [Guided documentation](https://goa.design/docs/2-goa-ai/) — start with agents, MCP, or registries.
- [Framework overview](docs/overview.md) — how design, generation, runtime, and engines fit together.
- [Composable prompt management](docs/prompts.md) — declarative templates, typed renderers, scoped overrides, and tracing.
- [DSL reference](docs/dsl.md) and [runtime reference](docs/runtime.md) — exact contracts and supported choices.
- [Architecture](DESIGN.md) — ownership and execution flows for contributors.
- [Go package reference](https://pkg.go.dev/goa.design/goa-ai) and [release notes](https://github.com/goadesign/goa-ai/releases).
## Contributing
Issues and PRs are welcome. Include a Goa design, failing test, or clear
reproduction when reporting behavior. See [AGENTS.md](AGENTS.md) for repository
guidelines.
Run `make setup` once after cloning or when `.tool-versions` or `.go-install`
changes. It installs the exact protobuf compiler and Go generators used by CI.
Normal `make` targets verify those versions before building or generating code.
## License
MIT License (C) Raphael Simon and the [Goa community](https://goa.design).