Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

Beyond the readOnlyHint annotation, the description adds substantial behavioral context: it returns specific fields, is the truth anchor for price consistency, indicates it is free tier and public data, and includes a disclaimer. It does not cover error cases or rate limits, but for a simple read-only getter, it is quite transparent.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Is the description appropriately sized, front-loaded, and free of redundancy?

The description is two sentences but packed with value: purpose, output shape, usage, source, and disclaimers. It is front-loaded with the truth-anchor framing and has no unnecessary words. Every sentence earns its place.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

Given the tool has one parameter, no output schema, and minimal annotations, the description is quite complete. It covers the return value shape, its authoritative nature, usage context, and data source. Slight gaps include error handling and specific coin format, but overall it is sufficient for a simple getter.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

The schema has 0% description coverage and only one parameter, 'coin'. The description merely says 'for a coin', which almost repeats the parameter name without adding format, example values, or accepted conventions. It does not compensate for the lack of schema information.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Does the description clearly state what the tool does and how it differs from similar tools?

The description clearly states what the tool does: it returns the canonical current price (live exchange mid) for a coin. It distinguishes itself from siblings by claiming to be the single source of truth that all other tools should agree with, and it specifies the output format.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Does the description explain when to use this tool, when not to, or what alternatives exist?

The description provides explicit usage guidance: use this tool to sanity-check any analytic payload and discount prices from tools that disagree materially. It does not name alternative tools explicitly, but it makes the appropriate context clear without needing exclusions.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.