feat(go): publish per-tool JSON output schemas (RC3-032 sub-part e) - #90
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Wire mcp.Tool.OutputSchema for all 21 registered tools, using the go-sdk's native OutputSchema field (part of the standard tools/list response every MCP client already fetches) rather than a new introspection tool or endpoint. Schemas are hand-authored raw-JSON constants (mirroring the existing input-schema convention) derived from reading each handler's actual return shape, checked into schemas/tools-output-snapshot.json with a TestOutputSchemaParityWithSnapshot test guarding drift, same pattern as the existing input-schema snapshot test. Deliberately permissive by design: no "required", no "additionalProperties": false anywhere, since a tool can return either its rich success shape or a slim structured-error shape (no provider configured, bad input) depending on runtime state, and both must validate against the same schema. In this codebase every handler builds CallToolResult.Content by hand and returns a nil structured-output value, so the SDK's own applySchema output validation never fires at call time regardless — these schemas are advertised metadata, not a runtime enforcement gate. internal/server/output_validation_test.go adds the missing check that gap otherwise leaves uncovered: it drives real success-path tool calls through an in-process MCP session and independently validates the returned JSON against each tool's OutputSchema via the go-sdk's own jsonschema resolve/validate, plus a negative-control test proving that check actually rejects a bad payload rather than passing vacuously. Covers get_price (compute, size_gb, iops, mbps), get_prices_batch, compare_prices, get_price_by_sku, estimate_bom, estimate_unit_economics, compare_bom, compare_bom_regions, find_cheapest_region, and find_available_regions.
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Summary
mcp.Tool.OutputSchemafield (already part of the standardtools/listresponse) — no new tool/endpoint needed, since every MCP client already fetches that listing.schemas/tools-output-snapshot.jsonwith a parity test, mirroring the existing input-schema convention.required, noadditionalProperties: falseanywhere — a tool can return either its rich success shape or a slim structured-error shape depending on runtime state, and both must validate against the same schema.CallToolResult.Contentby hand and returns anilstructured-output value, so the SDK's own output-schema validation never fires at call time.internal/server/output_validation_test.gofills that gap — it drives real success-path calls through an in-process MCP session and independently validates the JSON against each tool's schema (plus a negative-control test proving the check isn't vacuous).Test plan
go build ./...,go vet ./...cleango test ./... -count=1— all packages passTestAllToolsPresent/TestSchemaParityWithSnapshot/TestDescriptionParityWithSnapshot/TestOutputSchemaParityWithSnapshotall passoutput_validation_test.go: 14 success-path tests + 1 negative-control test, all passrequired/additionalProperties: falseanywhere in the 21 output schemas (grep, zero matches)