What this tool does
Tool Calling Validator checks OpenAI, Anthropic, and MCP tool-call payloads, argument shapes, and schema alignment.
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✅ Tool Calling Validator
Validate OpenAI, Anthropic, and MCP tool definitions or tool-call instances. Get precise missing-field paths, typed errors, examples, and copyable JSON reports.
What this checks
- Provider-specific wrapper shape: OpenAI tool definitions/calls, Anthropic tool/tool_use blocks, and MCP inputSchema definitions.
- Required names, descriptions, argument/input placement, and JSON-string vs object differences.
- JSON Schema basics: root object type, properties object, required fields declared in properties, enum arrays, nested items, and suspicious loose schemas.
- Typed path-specific errors such as
REQUIRED_FIELD_NOT_DECLARED,INVALID_ARGUMENTS_JSON, andROOT_SCHEMA_NOT_OBJECT.
Tool-calling contract workflow
Step 3: validation. Validate final tool definitions and sample calls here after drafting a schema in Tool Schema Generator or wrapping an existing schema in JSON Schema to Tool Definition.
Use the deterministic report to protect agent discoverability and API compatibility: provider wrappers, tool-call fixtures, and copied JSON summaries can be checked before any model or external service sees them.
Agent Contract Reliability
Compare a saved and current schema, validate representative arguments, and get one bounded retry-safety hint. Nothing is executed.
Why it is useful
It helps agent developers catch missing fields, wrong types, malformed JSON, and mismatches between tool definitions and calls before the payload reaches a model or runtime.
How it works
The browser parses the JSON, applies provider-specific rules, then validates the embedded JSON Schema shape and required fields with path-specific issues.
Best input
Paste one exact tool definition or one representative tool-call JSON object, then choose the matching mode.
Agent tip
Use the copied JSON summary in tests or runtime guardrails; prompt instructions alone cannot guarantee valid tool calls.
Privacy note
Validation happens locally in your browser.
Important limitation
A valid payload shape does not prove the tool call is safe, authorized, idempotent, or semantically correct.
Quick answers
Can this prevent bad tool use?
It catches structure problems, but policy, authorization, rate limits, and side-effect checks must happen elsewhere.
Does it execute tools?
No. It only validates JSON structure and schema shape.
Common Use Cases
Validate tool schemas before using them in agents
Check OpenAI, Anthropic, or MCP definitions for missing names, loose root schemas, and required fields that are not declared in properties.
Debug malformed tool calls from LLMs
Paste a failed OpenAI tool call or Anthropic tool_use block to find bad argument JSON, wrong wrapper types, or object-vs-string mistakes.
Create copyable validation fixtures
Export the JSON summary or fixed example into tests so agent tool contracts fail fast instead of failing at runtime.
Agent MCP and tool schema workflow
Draft MCP client config, generate tool schemas, convert JSON Schema into provider tool definitions, and validate tool-call payloads before wiring an agent.