dsh-gemini-tool-schema

Normalize the tool schemas sent to the model into the strict OpenAPI 3.0 subset that Gemini's function declarations accept. A TypeScript plugin for DeepSeek Harness.

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The problem

Strict providers accept only a subset of JSON Schema. Google Gemini's functionDeclarations[].parameters rejects the whole request (HTTP 400) when:

Real error	Offending schema	Source
schema didn't specify the schema type field	{ anyOf: [{type:'string',…}, {type:'null'}] } — no type	Playwright MCP browser_emulate_media.colorScheme (z.string().nullable())
properties[v_types].items: missing field	{ type: 'array' } — no items	Lingshu MCP lingshu_cg / lingshu_stg (19 params)
properties[permission].enum[3]: cannot be empty	enum: [..., '']	DSH built-in task_board_update.permission

All three are legal elsewhere, which is why the failure only shows up on a Gemini-flavoured route.

Why a Harness hook

An MCP proxy only reaches the servers it wraps. Built-in tools and tools registered by other plugins never cross an MCP transport, so normalizing at Harness assembly time is the only fix that covers every tool at once.

Install

git clone https://github.com/ChenXu233/dsh-gemini-tool-schema.git
cd dsh-gemini-tool-schema && npm install && npm run build

Append to <DSH home>/profiles/<profile>/cordis.patch.yml:

- insert:
    - id: gemini-tool-schema
      name: '/absolute/path/to/dsh-gemini-tool-schema/dist/index.js'
      config:
        mode: list
        apis: ['gemini', 'google', 'vertex']

Or npm install dsh-gemini-tool-schema and mount it by package name.

Configuration

Field	Default	Meaning
mode	list	all every request · list matching APIs only · off disabled
apis	['gemini','google','vertex']	API patterns, compiled as regular expressions
unknownApi	apply	When the route cannot be read: apply or skip
itemsFallback	{type:'string'}	Element schema for arrays that omit items
nullable	true	Emit nullable: true for null unions
dryRun	false	Report and lint, but send the original schemas
logFile / logLevel	none / info	One diagnostic line per assembly
dumpDir / dumpSchemas	none / true	Dump the model-facing tool set for offline auditing

Patterns match against provider/model (e.g. gemini-lumiya/gemini-4-argon) and accept substring, regex, and /pattern/flags forms; an entry that does not compile degrades to a case-insensitive substring match. '*' matches everything, or set mode: all.

Rules

Every node gets a type; every array gets items; enum entries are never empty (and const cannot reintroduce one); $ref/$defs are inlined cycle-safely; unsupported keywords are stripped and the remaining scalars pass an allow-list; required is narrowed to real properties.

Development

npm test        # Node ≥22.6 runs the TS tests directly — 36 tests
npm run build   # tsc → dist/

License

MIT © 2026 ChenXu233