[josemontespg]

Summary

Adds the updateDataModel data function to the v1 MCP catalog and @a2ui/catalog-mcp, writing each key-value pair of its updates object to the surface data model. Keys starting with / write to absolute paths, while relative keys resolve against the calling data context, such as the current row of a template list.

updateDataModel is declared in catalogs/mcp/v1/catalog.json, registered on mcpCatalog, and exported as UpdateDataModelApi and UpdateDataModelImplementation for hosts that compose their own catalogs. Every key is validated before anything is written (rejecting empty keys and __proto__, constructor, or prototype segments), objects and arrays are cloned before storage, and @path or @call objects inside values are stored as plain data rather than evaluated as expressions.

Changes

• typescript/catalogs/mcp/src/functions/update_data_model.ts and update_data_model.test.ts: implement UpdateDataModelApi and UpdateDataModelImplementation with path validation and unit tests.
• typescript/catalogs/mcp/src/catalog.ts and src/index.ts: register UpdateDataModelImplementation on mcpCatalog and export UpdateDataModelApi and UpdateDataModelImplementation.
• catalogs/mcp/v1/catalog.json and typescript/catalogs/mcp/src/catalog.test.ts: declare updateDataModel in the v1 catalog schema and check parity with mcpCatalog.
• catalogs/mcp/README.md, typescript/catalogs/mcp/README.md, CHANGELOG.md: document updateDataModel and its path validation rules.

Verification

• yarn workspace @a2ui/catalog-mcp run test and yarn workspace @a2ui/catalog-mcp run lint: node and karma test suites pass, including update_data_model.test.ts and catalog parity checks.
• specification/v1_0/test/run_tests.py and ./scripts/fix_format.sh --check pass.

[gemini-code-assist]

Code Review

This pull request introduces three new data functions (parseJson, jmespath, and updateDataModel) to the A2UI MCP catalog, enabling surfaces to process headless tool outputs and write them to the data model. It also adds a helper to settle pending asynchronous arguments, comprehensive tests, schema updates, and documentation. Feedback suggests implementing a two-pass validation approach in updateDataModel to prevent prototype pollution and ensure atomic updates.

[ditman]

As we decided in #3153 and implemented in #3171, general-purpose data transformation functions (parseJson, jmespath, updateDataModel) and the jmespath dependency should not live in catalogs/mcp/v1/catalog.json, conformance/core/catalog.yaml, or @a2ui/catalog-mcp.

Putting these into the v1 MCP catalog specification and conformance suite would require every client SDK implementing the MCP catalog (TypeScript, Flutter/Dart, Swift, etc.) to pull in a third-party JMESPath dependency and implement general ETL functions that are not specific to the MCP protocol. Instead, these functions should remain in the sample application that needs them (samples/community/mcp/a2ui-over-mcp-filesystem).

Note: The fix in typescript/catalogs/mcp/src/functions/callMcpTool.ts (importing DynamicStringSchema and DynamicValueSchema from @a2ui/web_core/v1_0 so @path/@call tool arguments validate in v1.0) is great — please extract that into its own small PR (or fold it into #3577 / #3578) and close this PR.

[ditman]

We discussed this offline and I was persuaded of letting some of these functions back in the catalog, even if they aren't directly required for the component to work, they may be generally helpful.

Please, update the documentation to ensure users know how to add their custom functions, we don't want a explosion of random functions becoming part of the catalog.