| name | connector_creator_skill |
| description | Create new connectors (CONNECTOR.md configs that connect the framework to an MCP server), improve/optimize existing connectors, evaluate connector quality, and — when needed — build a new MCP server to connect to. Use this whenever the task involves adding a connector for an MCP server, writing/editing a CONNECTOR.md, evaluating whether a connector's actions let an agent accomplish tasks, or building an MCP server from scratch (Python FastMCP or Node/TS). MetaAgent uses it to orchestrate the create→evaluate→improve loop across sub-agents. |
| version | 1.0.0 |
| type | ["orchestrator","worker"] |
| license | See LICENSE.txt (server-building guidance adapted from Anthropic mcp-builder) |
| category | meta |
| requirements | ["cpu"] |
| metadata | {} |
Connector Creator
A single skill for the full lifecycle of connectors — the framework's bridge to MCP (Model Context Protocol) servers. A connector is a CONNECTOR.md that points at an MCP server and declares which of its actions (tools) the framework exposes. This skill covers creating, improving, and evaluating connectors, and — for the case where no server exists yet — building an MCP server to connect to (adapted from Anthropic's mcp-builder).
Two directions, don't confuse them:
- A connector CONSUMES an MCP server — a client-side config (
CONNECTOR.md: a URL/transport + a list of actions). This is the common case (e.g. connecting to a hosted server like PubMed).
- An MCP server EXPOSES tools — server-side code. You only build one when you need to wrap your own API as MCP; then you still write a
CONNECTOR.md to connect to it.
How this skill is used — four roles, one body of knowledge
- MetaAgent (orchestrator role) — drives the create→evaluate→improve loop, dispatching the sub-agents and running with-connector vs baseline probes. See Orchestration.
- connector_generate_agent — reads Creating a connector (and Building an MCP server when the server doesn't exist yet).
- connector_optimize_agent — reads Improving a connector.
- connector_evaluate_agent — reads Evaluating a connector.
The three sub-agents are headless: each runs one phase autonomously and returns a result. There is no human-in-the-loop review; the evaluate agent is the automated grader, and the optimize agent iterates on that signal.
Framework conventions (read once)
- Connectors live in
{extension_root}/connector/{connector_name}/ (generated) or agentevolver/connector/default/{connector_name}/ (defaults).
- A connector directory:
{connector_name}/
├── CONNECTOR.md # REQUIRED — YAML frontmatter (connection + actions) + markdown body (module intro + per-action docs)
└── references/ # optional — extra docs the agent READs as needed
- Naming: the frontmatter
name (registry key) follows the <directory>_connector convention — directory pubmed → name: pubmed_connector. Keep it snake_case.
- Portable stdio connections: never hard-code machine-specific absolute paths. Use
command: python and a relative script path in args (e.g. server.py, relative to the connector directory). The connector manager resolves these at load time — command → the running interpreter (sys.executable), and the relative *.py → an absolute path under the connector directory — so the same CONNECTOR.md works on any machine/checkout/env. (streamable_http/sse connectors carry only a url and need no paths.)
- CONNECTOR.md frontmatter — required:
name, description, version, type, plus connection and actions:
---
name: pubmed_connector
description: PubMed — search biomedical literature, fetch article metadata and full text.
version: 1.0.0
type: worker
permission_mode: read_only
connection:
transport: streamable_http
url: https://pubmed.mcp.claude.com/mcp
actions:
- search_articles
- get_article_metadata
- get_full_text_article
---
The body below the frontmatter is a short module intro plus a per-action section documenting what each action does and its arguments — this is what an agent reads to call the connector.
- Registration is automatic via a hook: after writing/editing the files, include the connector directory path in your
done_tool reasoning — the registration hook picks it up.
Creating a connector
Start from the template: read references/connector_md_template.md, copy it to the connector directory, and fill in the connection + actions.
The common case: an MCP server already exists (hosted, or someone gives you a URL/command) and you write a CONNECTOR.md for it.
1. Identify the server and how to reach it
From the task, determine the connection: transport (streamable_http / sse for a URL endpoint, stdio for a local command) and the url (or command + args for stdio).
2. Discover the server's actions
Connect to the server and list the tools it exposes — don't guess. Use the bundled probe:
python {skill_dir}/scripts/connections.py <transport> <url-or-command>
scripts/connections.py is a lightweight MCP client (stdio/sse/streamable_http) that opens a session and lets you enumerate the server's tools and their input schemas. Record the action names and argument schemas — these become the actions list and the per-action docs.
3. Design the action surface
Follow the MCP tool-design principles in references/mcp_best_practices.md:
- Prefer clear, action-oriented names; keep descriptions concise.
- Expose the actions that let an agent accomplish real tasks; you don't have to surface every raw endpoint.
- Note filtering/pagination so agents can keep results focused.
4. Write CONNECTOR.md
Fill the frontmatter (connection + actions) and write the body: a one-paragraph module intro, then a section per action with what it does, when to use it, and arguments (from the discovered schema). Keep the description (frontmatter) both what-it-does and when-to-use, a little pushy so agents reach for it.
Then put the connector directory path in your done_tool reasoning so the registration hook installs it.
If the server doesn't exist yet
If the task requires wrapping an API that has no MCP server, first Build an MCP server (next section), host/run it, then come back and write the CONNECTOR.md pointing at it.
Building an MCP server
(Adapted from Anthropic's mcp-builder. Only needed when no server exists to connect to.)
Creating a high-quality MCP server is a four-phase process. The quality of a server is measured by how well it lets an agent accomplish real-world tasks.
Phase 1 — Research & planning
- Understand modern MCP design: balance comprehensive API coverage with focused workflow tools; use clear, prefixed, action-oriented tool names; return concise, filterable results; write actionable error messages. See
references/mcp_best_practices.md.
- Study the MCP spec (start at
https://modelcontextprotocol.io/sitemap.xml; fetch pages with a .md suffix) and the framework docs for your language.
- Plan the tools before writing code.
Phase 2 — Implementation
- Python (FastMCP): follow
references/python_mcp_server.md.
- Node/TypeScript (MCP SDK): follow
references/node_mcp_server.md.
- Set up the project, core infrastructure, then implement the tools with clear schemas and error handling.
Phase 3 — Review & test
- Check code quality; build and run the server; connect to it with
scripts/connections.py and confirm the tools list and behave as intended.
Phase 4 — Evaluations
- Create ~10 evaluation questions and measure the server (see Evaluating a connector and
references/evaluation.md).
Once the server runs, write a CONNECTOR.md for it (see Creating a connector).
Evaluating a connector
Goal: measure whether the connector's actions actually let an agent accomplish tasks — empirically, not just by reading the docs.
Static check (always)
Read the CONNECTOR.md and score it: are the required frontmatter fields present (connection, actions); is each action documented with purpose + arguments; does the description state what-it-does and when-to-use. Use inspect_connector_tool to confirm the connector is registered and to get its connection, actions, and directory. Validate structure with:
python {skill_dir}/scripts/validate_connector.py <connector_dir>
Connection check
Confirm the server is reachable and exposes the declared actions — connect with scripts/connections.py and compare the live tool list against the actions in the frontmatter. Flag missing or undocumented actions.
Empirical check (with-connector vs baseline)
The heart of quantitative evaluation is: do the connector's actions help versus not having them? There is no separate eval tool — MetaAgent runs the comparison by dispatching agents (see Orchestration). For each realistic test task:
- with-connector run: dispatch
general_agent with the connector available.
- baseline run: dispatch
general_agent without it.
Compare task success. See references/evaluation.md for the evaluation methodology (writing good task questions, judging tool use). Produce a scored report: static + connection + empirical, with concrete improvement suggestions.
Improving a connector
Given evaluation results, make the connector better. Edit its CONNECTOR.md:
- Fix action coverage — add missing actions the agent needed, or drop noisy ones it never uses.
- Sharpen per-action docs — clarify arguments and when-to-use so the agent calls them correctly; add examples for tricky ones.
- Tune the description for triggering (what-it-does + when-to-use, a little pushy).
- Keep it lean and explain the why in docs rather than piling on rigid rules.
Read the transcripts from the test runs, not just the outputs — if the agent misused an action or couldn't find the right one, that points at a doc or coverage fix. Re-register the edited connector by putting its CONNECTOR.md path in your done_tool reasoning.
Orchestration (for MetaAgent)
You own the create→evaluate→improve loop; you dispatch the sub-agents rather than doing the phases yourself:
- Generate — dispatch
connector_generate_agent with the intent (server URL/command + what it should expose). It probes the server, writes the CONNECTOR.md, and registers it.
- Evaluate — dispatch the with-connector and baseline runs, then
connector_evaluate_agent to grade:
- with-connector: a
general_agent sub-task that has the connector available.
- baseline: a
general_agent sub-task without it.
Then dispatch connector_evaluate_agent to grade the connection, coverage, and task success.
- Improve — dispatch
connector_optimize_agent with the evaluation results. It edits and re-registers.
- Repeat — go back to step 2 until the connector reliably helps.
Keep a plan/todo of the loop so you don't lose track across rounds.
Reference files
references/connector_md_template.md — the CONNECTOR.md skeleton (frontmatter connection/actions + per-action docs).references/mcp_best_practices.md — MCP tool-design principles (naming, context, errors).references/python_mcp_server.md / references/node_mcp_server.md — how to build an MCP server.references/evaluation.md — how to write evaluation questions and judge an MCP server/connector.scripts/connections.py — lightweight MCP client (stdio/sse/streamable_http) to probe a server's tools.scripts/validate_connector.py — fast structural validation of a CONNECTOR.md.
Core loop, one more time: identify the server → discover its actions → write the CONNECTOR.md → run an agent with the connector (and a baseline) on realistic tasks → evaluate → improve → repeat until it reliably helps.
