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

Annotations already declare readOnlyHint, idempotentHint, and destructiveHint false. The description adds valuable context beyond those: verified source (crt.sh), 4-hour caching, unsupported input types, and a fallback feedback path. This gives the agent a concrete behavioral model rather than merely restating the 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?

The description is front-loaded with the core purpose and key safety traits, then layers limitations, use case, alternative, source, cache, and feedback instructions. It is longer than minimal, but every sentence adds decision-relevant information; the feedback boilerplate is the only slightly repetitive part.

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 one-parameter tool with an output schema, the description is complete: it specifies inputs, limitations, return contents, source, cache behavior, when to use it, and when to use a sibling. Nothing an agent needs to call or interpret this tool correctly is missing.

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 already documents the domain parameter with 100% coverage, so the baseline is 3. The description adds extra semantic constraints beyond the schema: 'Does not support IP addresses or wildcard domains' and reiterates the no-protocol format. This pushes it above baseline, though it does not need to do much more for a single-parameter tool.

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 starts with a specific verb and resource: 'Fetch SSL certificate history for a domain from Certificate Transparency logs.' It also enumerates the returned data (issuer, subject, validity period, Subject Alternative Names), making the tool's function unambiguous and distinct from siblings like RDAP or DNS lookup tools.

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?

It explicitly states when to use the tool: 'Use this to detect unexpected certificate issuance or audit certificate history.' It also names the alternative: 'Use domain_fetch_domain_rdap instead when you need registration data not certificate data,' and clearly states unsupported inputs (IP addresses, wildcard domains).

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