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

Annotations already cover readOnly, idempotent, non-destructive behavior, so the description doesn't need to restate those. It adds valuable context beyond the annotations: the crt.sh source, 4-hour cache, output ordering, and exactly which certificate fields are returned (issuer, validity dates, SANs). Minor gap: no mention of rate limits or failure behavior.

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, then layered logically: safety, parameter, return format, use cases, alternative, source, cache, and fallback. It is longer than necessary because of the boilerplate report_feedback block, but each component serves a real decision-making purpose.

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 tool with rich annotations and an output schema, the description covers everything needed to invoke it correctly: exact input format, return content and ordering, data source freshness, use cases, and the sibling alternative. Nothing relevant 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?

Schema description coverage is 100%, so the schema already fully documents the domain parameter, including the 'without protocol' example and required status. The description repeats the same information without adding substantive new semantics, so it sits at the baseline rather than exceeding it.

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 uses a specific verb-resource pair ('Fetch historical SSL certificate issuance') and identifies the data source (Certificate Transparency logs). It clearly distinguishes this from the sibling domain_fetch_ssl_certificate_chain by contrasting 'historical' with 'current certificate chain'.

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 gives explicit use cases: detecting domain hijacking or auditing unexpected historical issuance. It also names the exact alternative (domain_fetch_ssl_certificate_chain) and the condition for choosing it instead, plus a feedback fallback if the tool doesn't satisfy the user's need.

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