Serve runtime-observed output shapes for schemaless tools

[RhysSullivan]

Muscle memory for code mode: most tools declare no output schema, so tools.describe.tool() renders data: unknown and models guess response shapes (or dump whole payloads). This learns shapes from live responses and serves them where nothing was declared.

Learn — executor.execute folds every successful dynamic-tool payload into a bounded inferred shape (packages/core/sdk/src/shape-inference.ts): field names and broad types only, never values; wide objects collapse to additionalProperties so data-bearing keys (emails, ids) never persist; depth/width/union/size all capped. Merging across calls makes missing fields optional and unions divergent types.

Store — plugin_storage under a reserved system id (executor.shape-memory): already migrated in every host, tenant/owner-scoped, and untouched by catalog refresh (which wipes tool rows). In-memory read-through cache per executor; a row write happens only when a new observation changes the merged shape, so stable APIs converge to zero writes.

Serve — tools.schema substitutes the observed shape only when neither the catalog row nor projectToolSchema declares an output schema, rendered through the existing JSON-Schema→TS compiler. ToolSchemaView gains outputSchemaSource: "observed" + outputSchemaObservations, and describe.tool adds outputTypeScriptNote telling the model the fields are reliable but possibly incomplete (the compact TS render drops schema descriptions). The execute skill text documents the note.

Evidence — new e2e scenario shape-memory.test.ts passes on selfhost and cloud: schemaless OpenAPI tool describes as data: unknown, one live call teaches { issues: { id: number; title: string; open: boolean; }[]; total: number; }, next describe serves it with the provenance note. The cloud pass spans three separate HTTP requests, so it proves the cross-session persistence path, not just the in-memory cache. Unit: 14 inference tests, 2 executor integration tests, 1 invoker cold→warm test.

Out of scope (follow-ups) — MCP tools: the MCP plugin always synthesizes a CallToolResult envelope schema, so its generic structuredContent slot needs an envelope-aware splice in the MCP plugin's projection. Search results still carry no type signatures (separate change on the Tool row). No TTL on observed shapes: continued use keeps them fresh; an unused tool's shape can go stale after an upstream API change.

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