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

Annotations already cover read-only, idempotent, and non-destructive hints. The description adds meaningful context beyond annotations: it specifies the result is a 'bounded set' (respecting the limit parameter) and explicitly states 'This tool does not download the payload' – a safety-relevant behavior not derivable from annotations alone. No contradiction with 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?

Two sentences, no redundancy. The core purpose is front-loaded, and the safety note ('does not download') is efficiently included without extra verbiage. Every word 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 simple lookup tool with full schema coverage and rich annotations, the description covers the essential: purpose, input type, result scope, and a key behavioral caveat. It does not describe output format in detail (no output schema), but the phrase 'bounded set of associated URLs' is adequate. No missing prerequisites or critical constraints.

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%, and both parameters (hash, limit) are well-documented in the schema with precise format and constraint details. The description does not add new semantic value beyond the schema, so baseline 3 applies per calibration rules.

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 a specific verb ('Look up'), resource ('URLhaus metadata'), and input type (hash). It distinguishes from sibling tools by emphasizing hash-based lookup and bounded URL results, making it distinct from urlhaus_lookup_host, urlhaus_lookup_url, etc.

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 implies usage for hash-based payload lookups without explicitly comparing to alternatives. It states the input type (MD5/SHA-256) and result scope (associated URLs), giving clear context. However, it does not explicitly say 'use this when you have a hash' or exclude other lookup types, so slightly shy of full guidance.

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