Three tools with minimal but present schemas and descriptions. describe_schema and echo_toolcall have clear, concise descriptions (40-60 chars). subagent_query is underspecified. All three have input schemas, but parameter descriptions are absent, the schema shows structure but LLMs cannot infer what each field means. No output schemas documented. No error handling guidance. Tool names are reasonable (verb_noun pattern) but lack context about when to use each. This is a minimal reference implementation, not production-grade.

• Add descriptions to all parameters. For echo_toolcall.input, clarify: 'The value to echo back. Can be a plain string or an object with message (required) and metadata (optional) fields.' For subagent_query.question, add: 'The question to dispatch to the sub-agent. Should be a complete, self-contained query.'
• Document output schemas for each tool. E.g., describe_schema should return {schema_version: string, tools: array of {name, description}}. echo_toolcall should return {success: boolean, data: <echoed input>}. subagent_query should return {trajectory: array, final_answer: string}.
• Expand subagent_query description to 100-150 chars explaining purpose, expected input format, and what 'one-turn trajectory' contains. E.g., 'Dispatch a question to a sub-agent and receive its reasoning steps and final answer. Returns the full trajectory of tool calls and responses.'
• Add error handling to subagent_query description: 'If the sub-agent fails, returns error details and suggests retry or alternative approaches.'
• Consider splitting echo_toolcall's anyOf union into two separate tools (echo_string, echo_object) or add a discriminator field to guide LLM selection between variants.