Skill for authoring, validating, and debugging Naftiko Capability YAML files (spec v1.0.0-alpha1). Activate when the user wants to: write a new capability document, add or change authentication on a consumed API, configure orchestration steps or parameter mappings, set up a forward proxy, expose an MCP server or Skill server, configure external references for secrets, add a control port for health checks and metrics, enable OpenTelemetry observability, or run the Spectral linter. The Naftiko Specification defines modular, composable capabilities that consume external APIs and expose REST, MCP, Skill, or Control adapters.
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Skill for authoring, validating, and debugging Naftiko Capability YAML files (spec v1.0.0-alpha1). Activate when the user wants to: write a new capability document, add or change authentication on a consumed API, configure orchestration steps or parameter mappings, set up a forward proxy, expose an MCP server or Skill server, configure external references for secrets, add a control port for health checks and metrics, enable OpenTelemetry observability, or run the Spectral linter. The Naftiko Specification defines modular, composable capabilities that consume external APIs and expose REST, MCP, Skill, or Control adapters.
allowed-tools
["Read","Write","Bash","Glob"]
Overview
The Naftiko Framework lets you declare capabilities — functional units that
consume external APIs and expose adapters (REST, MCP, Skill). A capability
is a single YAML file validated against the Naftiko JSON Schema (v1.0.0-alpha1).
Key spec objects you will work with:
Info — metadata: label, description, tags, stakeholders
Capability — root technical config; contains exposes, consumes, and aggregates
Exposes — server adapter: REST (type: rest), MCP (type: mcp), Skill (type: skill), or Control (type: control)
Aggregates — DDD-inspired domain building blocks; each aggregate groups reusable functions under a namespace. Tools and operations reference functions via ref
Observability — optional OTel configuration on the control adapter: trace sampling, propagation format, OTLP exporter endpoint
Script Steps — embed JavaScript, Python, or Groovy transformations between API calls using sandboxed GraalVM engines. Scripts read step results via bound variables and produce output through a result variable
Binds — variable injection from file (dev) or runtime (prod)
Namespace — unique identifier linking exposes to consumes via routing
Canonical sources (read these, never duplicate them):
Match the user's situation to a story reference. Each story explains why
(the user's problem), what (the Naftiko pattern), and points to the spec
for how.
Situation
Action
"I want to combine several APIs into a single reusable service"
Read references/reusable-capability.md
"I want to expose this API as an MCP server, including tools, resources, and prompts"
Read references/wrap-api-as-mcp.md
"I want to proxy an API today and encapsulate it incrementally"
Read references/proxy-then-customize.md
"I want to chain multiple HTTP calls to consumed APIs and expose the result into a single REST operation"
Read references/chain-api-calls.md
"I need to go from local test credentials to production secrets"
Read references/dev-to-production.md
"I want to define a domain function once and expose it via both REST and MCP"
Use aggregates with ref — read references/design-guidelines.md (Aggregate Design Guidelines)
"I want to add health checks, Prometheus metrics, or trace inspection"
Read references/control-port-observability.md
"I want to enable OpenTelemetry distributed tracing and RED metrics"
Read references/control-port-observability.md
"I want to transform data between API calls using JavaScript, Python, or Groovy"
Read references/inline-script-step.md
"I want to prototype a tool or endpoint before the backend exists" or "I want to return static or dynamic mock data"
Read references/mock-capability.md
"I want to build a full-featured capability that does all of the above"
Read all stories in order, then use assets/capability-example.yml as structural reference
"I have a YAML validation error"
Run scripts/lint-capability.sh — see Lint workflow below
"I'm done writing — what should I check before shipping?"
Read references/design-guidelines.md, then run lint
If the user's intent does not match any story, read the canonical
Specification directly.
Workflows
Edit a Capability
Analyze and propose. Infer the story from context (user prompt, open
files, existing capabilities). Read that story file, then present a
capability outline for the user to validate. Only ask what you cannot infer.
Scaffold. Copy assets/capability-template.yml. The document must
begin with naftiko: "1.0.0-alpha1".
Fill exposes. Choose the adapter type (REST, MCP, or Skill) and
follow the pattern from the story. For REST operations, use call +
with (simple) or steps + mappings (orchestrated) — never both.
Fill consumes. For each external API: set type: "http", a unique
namespace (kebab-case), baseUri (no trailing slash), resources,
and operations. Add authentication if needed.
Add binds if secrets or environment variables are needed.
Use location: "file:" for dev; remove it for prod.
Review. Read references/design-guidelines.md and check your
document against the design guidelines.
Validate. Run bash scripts/lint-capability.sh path/to/capability.yml.
Fix any errors, then re-lint until clean.
Lint a Capability
Run the lint script:
bash scripts/lint-capability.sh path/to/capability.yml
Do NOT regenerate or modify this script.
Spectral reports errors and warnings with rule names. Common rules:
naftiko-control-port-singleton-and-unique (error) — more than one control adapter, or port collision
naftiko-control-address-localhost-warning (warn) — control port bound to non-localhost
For the full rule list, read the Spectral ruleset file directly.
Fix and re-lint. Repeat until clean.
Mock a Capability
Use mock mode when the upstream API does not exist yet, or you want to
prototype a contract-first design. Read references/mock-capability.md
before writing any mock output parameters.
Key rules:
Omit call, steps, and the entire consumes block — they are not
needed for a pure mock capability.
Use value on MappedOutputParameter for static strings
(value: "Hello") or Mustache templates (value: "Hello, {{name}}!").
Do NOT use const — it is schema-only and is never used at runtime.
Mustache placeholders in value are resolved against the tool's or
endpoint's input parameters by name. Only top-level input parameter
names are in scope — no nesting, no with remapping.
value and mapping are mutually exclusive on a scalar output
parameter — never set both.
Object and array type output parameters in mock mode must carry
value on each leaf scalar descendant; the container itself has
no value.
When the mock is ready to be wired to a real API, add consumes,
replace value with mapping, and add call or steps — the
exposed contract does not change.
and trustedHeaders (at least one entry).
MCP tools must have name and description (unless using ref, in which
case they are inherited from the referenced aggregate function). MCP tool input
parameters must have name, type, and description. Tools may declare optional
hints (readOnly, destructive, idempotent, openWorld) — these map to
MCP ToolAnnotations on the wire.
ExposedOperation supports three modes (oneOf): simple (call +
optional with), orchestrated (steps + optional mappings), or
ref (ref to an aggregate function). Never mix fields from
incompatible modes.
Do not modify scripts/lint-capability.sh unless explicitly asked —
it wraps Spectral with the correct ruleset and flags.
Do not add properties that are not in the JSON Schema — the schema
uses additionalProperties: false on most objects.
Every exposed inputParameter must be referenced in at least one
step's with block or mapping — orphan parameters bloat the API
surface and confuse consumers.
Every consumed outputParameter must be referenced in the exposed
part (via mappings, or outputParameters) — unreferenced
outputs are dead declarations that add noise without value.
Do not prefix variable names with the capability, namespace, or
resource name — variables are already scoped to their context.
Redundant prefixes reduce readability without adding disambiguation.
When using ref on MCP tools or REST operations, the ref value must
follow the format {aggregate-namespace}.{function-name} and resolve
to an existing function in the capability's aggregates array.
Do not chain ref through multiple levels of aggregates — ref
resolves to a function in a single aggregate, not transitively.
Aggregate functions can declare semantics (safe, idempotent, cacheable).
When exposed via MCP, the engine auto-derives hints from semantics.
Explicit hints on the MCP tool override derived values.
Do not duplicate a full function definition inline on both MCP tools
and REST operations — use aggregates + ref instead.
In mock mode, use value on output parameters — never const.
const is a JSON Schema keyword retained for validation and linting
only; it has no effect at runtime.
In mock mode, Mustache templates in value fields resolve only against
top-level input parameter names. Do not reference with-remapped
consumed parameter names — those are not in scope for output resolution.
At most one type: "control" adapter is allowed per capability. Its
port must not collide with any business adapter port.
The control port address should be localhost or 127.0.0.1 for
security. Binding to 0.0.0.0 exposes management endpoints externally.
The /metrics and /traces control port endpoints are configured under
observability.metrics.local and observability.traces.local respectively.
Observability is enabled by default — all enabled fields default to
true. Set enabled: false to disable specific endpoints or observability
entirely. They return 503 when the OTel SDK is not on the classpath.
When adding a control port, also add observability on the control
adapter if you want metrics and traces to produce data. Without it,
the local endpoints return empty or 503 responses.
The observability.exporters.otlp.endpoint field supports Mustache
expressions for binds (e.g. "{{OTEL_ENDPOINT}}"). Use binds to
keep exporter URLs environment-specific.
Script steps require a file property. language and location are
optional when Control Port defaults are configured via
management.scripting.defaultLanguage and management.scripting.defaultLocation.
Script dependencies are pre-evaluated in order before the main script.
Shared logic (helpers, constants) goes in dependencies.
The script must assign to the result variable to produce output.
Previous step results are bound as variables matching step names.
When management.scripting is configured on the Control Port,
defaultLanguage and defaultLocation serve as fallbacks — step-level
values take precedence.
allowedLanguages restricts which languages script steps may use.
If omitted, all three languages (javascript, python, groovy) are
allowed.
