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

With no annotations, the description carries full burden. It discloses that the tool is paid, returns an HTTP 402 payment challenge, and requires settlement for access. This adds value beyond basic read expectations, though it does not explicit state it is non-destructive.

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 concise, with three sentences each serving a distinct purpose: what the tool does, the payment mechanism, and the beta note. No wasted words.

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 no output schema, the description covers the return value fields (sponsor, max grant, etc.) and the payment flow sufficiently. It lacks error handling or authorization details but is adequate for a single-param tool.

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 single parameter 'subsidy_id' is described both in the schema (as a live jGrants id) and in the description (which provides example format). The description also explains what fields the record contains, adding meaning beyond the schema alone.

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?

Description clearly states that the tool retrieves the full raw record of a specific Japanese subsidy/grant program, listing key fields (sponsor, max grant amount, etc.). This distinguishes it from sibling tools like search_subsidies which would return a list.

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 explains the payment model (x402, cost, settlement) and the beta status, providing important context for usage. However, it does not explicitly state when to use this tool over alternatives, though the purpose implies it is for fetching a single detailed record.

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