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

Annotations already cover read-only/idempotent/non-destructive, but the description adds materially new behavior: it is free with no x402 challenge, so it should be called directly rather than through a payment flow, and the results are deterministic ("every check is reproducible from them"). It also gives the HTTP equivalent endpoint for parity.

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?

Front-loaded with the content list, which is the useful part, and the payment note follows. The payment clause is internally redundant ("no payment required" restated as "this tool is free"), and the trailing HTTP URL is auxiliary, but neither buries the key information.

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?

With no parameters, no output schema, and safety already covered by annotations, the remaining need is to tell the agent what it will get back and why it matters — the description enumerates the document's sections and asserts reproducibility. There is no material gap left for an agent deciding whether to call it.

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 tool takes zero parameters and the schema is empty, so there is nothing to disambiguate; baseline for a no-param tool is 4. Nothing in the description contradicts or is needed to interpret an empty input.

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?

States a specific resource (the published Reference Check criteria, reference-resolution/v1) and enumerates what it contains: identifier forms, type inference, ID normalization, adapters, comparison rules, verdict vocabulary, leg switches, scope line. An agent can immediately tell this is the specification document rather than the checker itself, distinguishing it from refcheck_check/refcheck_precheck.

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?

"Read these before paying for a check" gives an explicit trigger for calling this tool and implicitly positions the paid check as the downstream action. It doesn't name refcheck_check directly or state when-not-to-use, so it stops short of a full routing sentence.

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