The to_openapi spec was describing one OpenAPI path per alknet operation
— the inverse of from_openapi. That inverse is genuinely messy: the call
protocol's input is a flat JSON object, and generating a traditional
OpenAPI path entry (POST /fs/{path} with path param, body, query params)
requires reverse-engineering which fields are path/query/body — metadata
the call protocol doesn't carry. The three options (leaky HTTP metadata
on OperationSpec, fragile heuristics, manual annotation) are all messy.
ADR-042 replaces this with the gateway pattern (same as ADR-041 for
to_mcp): to_openapi generates 5 fixed endpoints (search, schema, call,
batch, subscribe) that gate access to the full operation registry. The
input is always a flat JSON body — no path/query/body split to
reverse-engineer. JSON Schema is already in the OperationSpec.
The per-caller API surface is the key advantage: /search is
AccessControl-filtered, so the client sees only what it can call. The
Gitea failure mode (dumping admin ops to every caller in a static
OpenAPI doc) is structurally impossible — the per-caller surface is the
default, not an afterthought. OpenAPI has no per-caller filtering
concept; the gateway pattern provides it through /search.
Gateway endpoint set:
- /search -> services/list (AccessControl-filtered, names + descriptions)
- /schema -> services/schema (full OperationSpec)
- /call -> call.requested (Query/Mutation, flat JSON body)
- /batch -> multiple call.requested (correlated IDs)
- /subscribe -> call.requested (Subscription, SSE) — the one endpoint
the MCP gateway excludes (MCP is request/response; OpenAPI/SSE
supports streaming)
A traditional per-operation-paths projection is additive (a deployment
that wants the nice Swagger UI builds it with HTTP-specific metadata),
not a replacement. The gateway is the default.
http-adapters.md to_openapi section rewritten: the gateway endpoint
set, per-caller filtering, error fidelity on the /call endpoint, and
the additive traditional projection. The 'Why' section adds the
flat->structured and per-caller-surface rationale.
README/overview ADR tables and the top-level README current-state note
updated for ADR-042.
