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

Description reiterates annotations (read-only, no side effects, idempotent) and adds constraints like no IP/wildcard support, verified source (crt.sh), and 4-hour cache. No contradictions.

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?

Every sentence adds value; no fluff. Clear hierarchy: purpose, parameter, usage, alternative, fallback. Well-structured within a single paragraph.

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?

Covers purpose, parameter constraints, usage guidance, caching, source verification, return value summary, and fallback agent gap reporting. Output schema exists so return value description sufficient.

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 has 100% coverage with one parameter described. Description adds constraint that domain must not include protocol and explicitly says 'Required.' plus 'Does not support IP addresses or wildcard domains,' which goes beyond schema.

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 verb 'Fetch' and resource 'SSL certificate history for a domain from Certificate Transparency logs'. It distinguishes from sibling tool 'domain_fetch_domain_rdap' by specifying when to use each.

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?

Explicitly states when to use ('detect unexpected certificate issuance or audit certificate history') and when not to use ('use domain_fetch_domain_rdap for registration data'). Also provides source and cache info.

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