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[GH-ISSUE #4993] VS Code MCP schema validation fails for mcp_rea_build_call_path #3085

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opened 2026-10-31 00:36:21 +00:00 by bsakaguchi · 3 comments

bsakaguchi commented

2026-10-31 00:36:21 +00:00

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Originally created by @Theminacious on GitHub (Oct 18, 2026).
Original GitHub issue: https://github.com/morluto/rea/issues/4993

Before submitting

I searched the open and closed issues for a related report.
I removed credentials, tokens, private paths, and sensitive target data.

Area

MCP or agent integration

Observed behavior

VS Code reports this error when validating the REA MCP tool:

Failed to validate tool mcp_rea_build_call_path: Error: tool parameters array type must have items.

REA is configured through the VS Code MCP registration using npx -y rea-agents@6.5.0 mcp. The error persisted after reloading VS Code. The REA doctor output reports the VS Code registration as healthy.

The observed error indicates a tool-schema validation failure. The exact malformed schema and root cause have not yet been confirmed.

Reproduction

Configure REA for VS Code using the command below.
Open the VS Code agent Configure Tools interface.
Observe the validation error for mcp_rea_build_call_path.
Reload VS Code and check again.

MCP server configuration:
command: npx
args: ["-y", "rea-agents@6.5.0", "mcp"]

The error persisted after reloading. The number of independent reproductions is unknown; no direct MCP protocol request or standalone schema reproduction has been captured.

Expected behavior

The MCP tool should expose a schema accepted by the client, or return a clear, actionable compatibility error. The expected schema for build_call_path has not yet been independently verified.

Impact and scope

The build_call_path tool cannot be validated in the current VS Code setup. Whether other REA tools are affected is not yet established. No target data or project files were modified as part of this troubleshooting.

REA version

6.5.0

Runtime and platform

Node.js 24.18.0; macOS (reported environment: macOS 15 arm64); VS Code version not yet recorded; Hopper detected by REA doctor. Hopper version not verified for this report.

Target and artifact context

Interface

MCP

Earliest failure stage

Request parsing or validation

Relevant output or evidence

Command or MCP request actually run:
npx -y rea-agents@latest --version
npx -y rea-agents@latest doctor --client vscode --json

Relevant result:
The version command returned 6.5.0. The doctor output reported the VS Code registration as healthy and Hopper as healthy. VS Code separately displayed the mcp_rea_build_call_path validation error.

Missing evidence:
The raw MCP tools/list response and the build_call_path inputSchema have not been captured, so the precise schema defect remains unverified.

Typed outcome or recovery expected

No response

Analysis or suspected cause

No response

Additional context

No response

Originally created by @Theminacious on GitHub (Oct 18, 2026). Original GitHub issue: https://github.com/morluto/rea/issues/4993 ### Before submitting - [x] I searched the open and closed issues for a related report. - [x] I removed credentials, tokens, private paths, and sensitive target data. ### Area MCP or agent integration ### Observed behavior VS Code reports this error when validating the REA MCP tool: Failed to validate tool mcp_rea_build_call_path: Error: tool parameters array type must have items. REA is configured through the VS Code MCP registration using `npx -y rea-agents@6.5.0 mcp`. The error persisted after reloading VS Code. The REA doctor output reports the VS Code registration as healthy. The observed error indicates a tool-schema validation failure. The exact malformed schema and root cause have not yet been confirmed. ### Reproduction 1. Configure REA for VS Code using the command below. 2. Open the VS Code agent Configure Tools interface. 3. Observe the validation error for mcp_rea_build_call_path. 4. Reload VS Code and check again. MCP server configuration: command: npx args: ["-y", "rea-agents@6.5.0", "mcp"] The error persisted after reloading. The number of independent reproductions is unknown; no direct MCP protocol request or standalone schema reproduction has been captured. ### Expected behavior The MCP tool should expose a schema accepted by the client, or return a clear, actionable compatibility error. The expected schema for build_call_path has not yet been independently verified. ### Impact and scope The build_call_path tool cannot be validated in the current VS Code setup. Whether other REA tools are affected is not yet established. No target data or project files were modified as part of this troubleshooting. ### REA version 6.5.0 ### Runtime and platform Node.js 24.18.0; macOS (reported environment: macOS 15 arm64); VS Code version not yet recorded; Hopper detected by REA doctor. Hopper version not verified for this report. ### Target and artifact context \ ### Interface MCP ### Earliest failure stage Request parsing or validation ### Relevant output or evidence Command or MCP request actually run: npx -y rea-agents@latest --version npx -y rea-agents@latest doctor --client vscode --json Relevant result: The version command returned 6.5.0. The doctor output reported the VS Code registration as healthy and Hopper as healthy. VS Code separately displayed the mcp_rea_build_call_path validation error. Missing evidence: The raw MCP tools/list response and the build_call_path inputSchema have not been captured, so the precise schema defect remains unverified. ### Typed outcome or recovery expected _No response_ ### Analysis or suspected cause _No response_ ### Additional context _No response_

bsakaguchi

2026-10-31 00:36:21 +00:00

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bsakaguchi commented

2026-10-31 00:36:22 +00:00

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@XinwangTao commented on GitHub (Oct 18, 2026):

The error "tool parameters array type must have items" points at a schema that serializes some parameter as a bare "type": "array" with no items. items is technically optional in JSON Schema, but VS Code's validator treats it as required, which is why the same tool passes REA's doctor yet fails in VS Code. To pin the root cause, capture the raw tools/list response for build_call_path (a single MCP handshake with logging, or a temporary dump of the serialized inputSchema is enough) — if the schema shows {"type":"array"} with no items, the fix is to emit items: {} (or the real element type) when building that tool's parameter schema. It'd also be worth scanning the other array-typed tools (anything taking args-style lists) for the same pattern, since a strict client will reject all of them the same way.

@XinwangTao commented on GitHub (Oct 18, 2026): The error "tool parameters array type must have items" points at a schema that serializes some parameter as a bare `"type": "array"` with no `items`. `items` is technically optional in JSON Schema, but VS Code's validator treats it as required, which is why the same tool passes REA's doctor yet fails in VS Code. To pin the root cause, capture the raw `tools/list` response for `build_call_path` (a single MCP handshake with logging, or a temporary dump of the serialized inputSchema is enough) — if the schema shows `{"type":"array"}` with no `items`, the fix is to emit `items: {}` (or the real element type) when building that tool's parameter schema. It'd also be worth scanning the other array-typed tools (anything taking `args`-style lists) for the same pattern, since a strict client will reject all of them the same way.

bsakaguchi commented

2026-10-31 00:36:23 +00:00

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@pablodiazjorge commented on GitHub (Oct 18, 2026):

This looks like the same root cause as #4985, where I counted the affected schemas: in 6.5.0, 228 array nodes without items across 23 tools, build_call_path among them, all from one shared fixed tuple advertised with prefixItems only. 204b9f3ac (fix(contracts): preserve array guidance across MCP schema profiles) gives those tuples an items schema, and it is in rea-agents-6.7.0, which is now latest on npm.

One thing specific to your setup: the VS Code registration pins ["-y", "rea-agents@6.5.0", "mcp"], so it will keep serving the 6.5.0 schemas even now that latest has moved. Changing the pin to rea-agents@6.7.0 (or rea-agents@latest) and restarting the server should clear the error.

Checked: on Windows 11, a source build of main 01cdbbdc5 advertises no array node without items, and src/domain/fixedTupleSchema.ts is unchanged between that commit and the rea-agents-6.7.0 tag. Not run: the published 6.7.0 package, VS Code, or macOS.

@pablodiazjorge commented on GitHub (Oct 18, 2026): This looks like the same root cause as #4985, where I counted the affected schemas: in 6.5.0, 228 `array` nodes without `items` across 23 tools, `build_call_path` among them, all from one shared fixed tuple advertised with `prefixItems` only. 204b9f3ac (`fix(contracts): preserve array guidance across MCP schema profiles`) gives those tuples an `items` schema, and it is in `rea-agents-6.7.0`, which is now `latest` on npm. One thing specific to your setup: the VS Code registration pins `["-y", "rea-agents@6.5.0", "mcp"]`, so it will keep serving the 6.5.0 schemas even now that `latest` has moved. Changing the pin to `rea-agents@6.7.0` (or `rea-agents@latest`) and restarting the server should clear the error. Checked: on Windows 11, a source build of main `01cdbbdc5` advertises no `array` node without `items`, and `src/domain/fixedTupleSchema.ts` is unchanged between that commit and the `rea-agents-6.7.0` tag. Not run: the published 6.7.0 package, VS Code, or macOS.

bsakaguchi commented

2026-10-31 00:36:23 +00:00

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@Theminacious commented on GitHub (Oct 18, 2026):

Verified on macOS with VS Code: updating the MCP configuration from rea-agents@6.5.0 to rea-agents@6.7.0 and reloading VS Code resolved the mcp_rea_build_call_path schema validation error.

The REA tools are now available without the reported validation error. Thanks for identifying the shared tuple-schema issue and confirming the fix in 6.7.0!

@Theminacious commented on GitHub (Oct 18, 2026): Verified on macOS with VS Code: updating the MCP configuration from `rea-agents@6.5.0` to `rea-agents@6.7.0` and reloading VS Code resolved the `mcp_rea_build_call_path` schema validation error. The REA tools are now available without the reported validation error. Thanks for identifying the shared tuple-schema issue and confirming the fix in 6.7.0!

bsakaguchi referenced this issue

2026-10-31 01:07:54 +00:00

[PR #3085] [CLOSED] fix(hopper): probe user Applications launcher on macOS #5603

bsakaguchi referenced this issue

2026-10-31 01:09:38 +00:00

[PR #3548] [MERGED] fix(hopper): skip non-file launcher candidates #5814