Status: frame-level draft · sole-witness-capped (≤0.85 frame, 0.5–0.6 on contested points). Resolves frontier #16; defers #20, #127.
An operation signature is what lets a tool route a concrete HTTP request to at most one
described operation. It generalises the 3.x path + method into a multi-aspect tuple over:
signature ⊆ { method, uri-template (incl. query), content-type, headers, request-body shape }
The mechanism is uniform and implicit across an API — there is no required per-API "signature style" declaration. (@0.5 — overrides an early unreconciled proposal; the riskiest claim here.)
Signatures are exposed at the ADA (the abstract description surface a tool consumes), produced by a DOM → ADA mapping. Both the DOM and the ADA are non-mandatory for tooling. The spec defines the signature mechanism by what the ADA must expose — working backward from the "request → operation" matcher a router needs — and bakes in only analysis whose cost is reasonable for the vast majority of APIs.
Per operation, the ADA exposes a normalised signature view (which aspects participate; literal vs variable structure). Across operations, the ADA exposes a three-valued collision verdict:
provably-disjoint | provable-collision | not-statically-determinable
Static ambiguity detection is a desideratum under explicit feasibility limits, not a guarantee and not a validation gate. 3.x templating may not permit full analysis; JSON Schema is not analyzable in the general case. The ADA therefore surfaces overlap (the three-valued verdict); it does not forbid it. Concrete-over-variable (specificity) precedence carries forward from 3.x, but is bounded — 3.x leaves param-vs-param superset and bidirectional overlap undefined.
What a tool should do about a detected collision (treat as invalid · apply precedence · honour an authored priority · strict-mode error) is left open (frontier, not resolved here). The recorded SIG lean is priority-as-last-resort.
This section defines matching (route a request to zero-or-one operation) only. Correlating (which response schema pairs with which request) is a separate concern.
parameterSchema or one schema per location (URL/header/body). The ADA fixes only the shape of exposure; this split is chosen afterward.