dsh-tool-json

中文

DSH JSON query tool plugin — JMESPath-inspired path queries (custom subset) with a zero-dependency recursive-descent parser.

Why

Handling JSON is a high-frequency operation for agents — API return values, config files, and tool outputs are JSON everywhere. The current approach spawns a bash subprocess to run node -e or jq, incurring subprocess overhead and string serialization costs every time.

DSH's built-in grep can do regex matching but cannot understand JSON structure. For {"items":[{"id":1}]}:

• grep only does string-level search, easily false-matching values, keys, or same-named keys in nested sub-objects
• json follows structured paths, matching only the specified path without confusing keys and values

Security model

Hand-written recursive-descent parser, no eval/new Function; Object.hasOwn prevents prototype-chain pollution (reading constructor/__proto__ does not trigger the prototype chain). Resource limits (uniformly enforced across both the object and string input paths):

• Query expression length ≤ 200 characters, parse depth ≤ 20 levels, array indices must be safe integers
• String input ≤ 1,000,000 bytes (UTF-8); input nesting depth ≤ 100
• Single wildcard projection ≤ 100,000 elements
• Only accepts JSON-compatible values (null/boolean/finite number/string/array/plain object; rejects undefined/BigInt/functions/Date/non-finite numbers)

Error classification (JsonQueryError): MISSING_PROPERTY (skipped inside projections), TYPE_MISMATCH/INDEX_OUT_OF_BOUNDS/INVALID_QUERY (thrown as-is), all with a unified json: prefix.

Cost model (AUDIT-JSON-03): input undergoes full validation (type/depth/bytes/cycles/enumerability) before every query — this is an intentional security cost; even querying a small field fully scans the input; timeoutMs cannot interrupt the synchronous validation.

Architecture

DSH Agent
    │ ctx.tools.register()
    ▼
src/index.ts（Cordis 插件入口 + action 分发）
    │
    ▼
src/query.ts
    ├── parseQuery() — 递归下降解析器（strict 语法 + 转义 + 上限）
    ├── executeQuery() — 执行器（错误分类 + 投影上限）
    └── normalizeInput() — 双形态输入 + assertJsonCompatible 校验

Tool declaration

ctx.tools.register(defineTool({
  name: 'json',
  parameters: {
    input: { type: 'json', required: true, description: 'JSON value or JSON string to query.' },
    query: { type: 'string', required: true, description: 'Path expression, e.g. "data.items[0].name".' },
  },
  output: { schema: { type: 'json' }, render: (_a, v) => [{ type: 'text', text: JSON.stringify(v) }] },
  execute: (args) => Promise.resolve(executeAction(args) as JsonValue),
  timeoutMs: 1000,
}))

input has two forms: an object passed directly (the model generates the argument directly, zero escaping) or a string (raw passthrough from bash/read); normalizeInput unifies normalization and validation.

Query syntax (JMESPath-inspired subset)

Semantic boundaries (intentionally incompatible with standard JMESPath, locked):

• Multi-level wildcards like items[*].tags[*] return nested arrays ([['a','b'],['c']]) without standard projection flattening
• Wildcards apply to arrays only; object field enumeration is not supported; non-object elements are skipped per projection semantics; legal null results are preserved
• Quoted properties support three escapes \\ \' \" (usable under any quoting form); illegal escapes error
• Only MISSING_PROPERTY is skipped inside projections; type/index/internal errors are thrown as-is

Not supported (low-frequency scenarios; fall back to bash + node): filters [?downloads > 1000], pipes |, function calls.

DSH 0.1.5-rc.1 compatibility (verified)

This plugin has been migrated to the DSH 0.1.5-rc.1 harness and fully verified in an isolated consumer of local harness 0.1.5-rc.1:

• Types/runtime: @deepseek-ai/cordis@^4.0.1 + @deepseek-ai/dsh-tools@>=0.0.1-rc.1 <0.2.0 + @deepseek-ai/dsh-invariants@>=0.0.1-rc.1 <0.2.0 (peer); no longer depends on unscoped cordis
• Standalone build: npm install (devDependencies are self-contained: typescript/vitest/@types/node) → npm run typecheck → npm test → npm run build → npm pack
• Consumption verification: tarball installed into the 0.1.5-rc.1 consumer → dsh --profile compat --dump-config shows this plugin's row → the tool actually registers and executes
• Startup: npx -p @deepseek-ai/dsh@next dsh web (lib production mode; do not install -g globally)

Version adaptation

• DSH version adapted: DSH 0.1.5-rc.1
• Bundle declaration: dsh.bundle in package.json (patch points to cordis.patch.yml) + exports fields
• Patch format: cordis.patch.yml uses the - insert: list (patches are id-targeted; a bare - id: entry reports entry not found)
• files: the published tarball contains lib/, src/, cordis.patch.yml

Installation

Plugin source repository: https://github.com/omdsh-dev/dsh-tool-json (public).

Profile Bundle (recommended)

Install this plugin as a standalone bundle into a profile (DSH 0.1.5-rc.1, npm):

# 交互式（web）profile
dsh plugin --profile web add github:omdsh-dev/dsh-tool-json
# 一次性任务（headless）profile —— dsh run 默认使用 headless
dsh plugin --profile headless add github:omdsh-dev/dsh-tool-json

The dsh.bundle.patch inside the package (pointing to cordis.patch.yml) automatically adds the plugin to the profile's layer stack after installation; the plugin's cordis.patch.yml inserts the tool-json entry via - insert:.

⚠️ web and headless are different profiles: installing into web does not automatically cover headless; dsh run uses the headless profile by default.

Install via npm pack tarball

npm pack    # generates dsh-tool-json-*.tgz
dsh plugin --profile web add ./dsh-tool-json-*.tgz
dsh plugin --profile headless add ./dsh-tool-json-*.tgz

Verify installation

dsh --profile web --dump-config | grep tool-json

Run verification

dsh run "使用 json 工具查询 {"a":{"b":1}} 的 a.b"

Manual installation and legacy compatibility

Only for legacy snapshots that do not support Profile Bundle, or plugin development/debugging environments:

1. Place into the monorepo: cp -r json ~/.dsh/source/master/packages/tools/json (development/debugging)
2. Add "@deepseek-ai/dsh-tool-json": "workspace:^" to apps/cli/package.json; add { "path": "./packages/tools/json" } to the references of tsconfig.host.json
3. pnpm install && pnpm run build
4. Insert the plugin in the profile's user-layer patch (~/.dsh/profiles/<name>/cordis.patch.yml):

- insert:
    - id: tool-json
      name: '@deepseek-ai/dsh-tool-json'

1. Verify: dsh --profile <name> --dump-config | grep tool-json

Note: patches are id-targeted — a bare - id: entry reports entry "xxx" not found; it must be wrapped in an - insert: list.

Usage

json { input: <JSON>, query: "items[0].name" }        → "hello"
json { input: <JSON>, query: "items[*].name" }         → ["a", "b"]（合法 null 保留）
json { input: <JSON>, query: "items['complex-key']" }  → "ok"

Known limitations

1. Read-only: cannot modify JSON fields (use str_replace_editor/write for in-place edits; a set mode may be considered for v2)
2. No filter expressions, no standard JMESPath projection flattening (see semantic boundaries)
3. Object-form input relies on the DSH parameter pipeline to guarantee lossless JSON

Testing

pnpm test

54 test cases (functionality, errors, attack payloads, object/string dual-form inputs, resource limits, and escaping boundaries). See the locally maintained design document for the full list.

License

MIT