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

Annotations only declare readOnly and openWorld; the description adds the data provenance (CertSpotter/CT), the fact that revocation status is only as fresh as the CRL publication time, the exact returned fields, and a full pricing model including that failed calls are free. That is genuinely decision-relevant context an agent cannot get from annotations.

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-loads the operation, then caveats, then price. Dense but every clause carries information; 'Revocation status is as of the CRL's publication time' slightly overlaps the nextUpdate mention but still 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?

For a single-parameter, read-only lookup with an output schema, the description covers source of truth, freshness limitation, the alternative it does not do (OCSP), and cost. An agent has everything needed to decide and call correctly.

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?

Schema coverage is 100% for the single domain parameter, so the baseline is 3; the description adds that the domain is used to derive the certificate and its CRL Distribution Point, clarifying what the input actually drives. No format edge cases (subdomains, wildcard certs) are discussed.

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 verb chain and resource: reads the CRL Distribution Point from a domain's current certificate, downloads the CRL, and reports serial-number presence plus thisUpdate/nextUpdate. It also explicitly scopes out OCSP, so an agent can distinguish this from other certificate tools without opening the schema.

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 opening clause establishes the precondition (a domain's current cert sourced from public CT data) and the 'OCSP is not queried' note draws a clear boundary against other revocation-checking paths. It stops short of naming a sibling tool or stating when a different security_* check would be preferable.

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