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
