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

Adds substantial context beyond annotations: pagination behavior ('Returns 25 at a time, newest first'), the page/next_page contract, authentication behavior ('Needs the person to sign in... asks the app to sign them in'), and safety ('It changes nothing'). This is richer than the readOnly/idempotent hints alone.

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-loaded with when to use, then pagination, filtering, alternative tool, auth, and safety. Every sentence is functional with no repetition or filler.

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?

Given the output schema exists and annotations cover safety, the description supplies everything an agent needs: trigger conditions, pagination mechanics, filtering, auth behavior, and the sibling alternative. Nothing essential 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 coverage is 100% so the baseline is 3, but the description adds practical usage: pass next_page back as page and filter with status using examples like ["failed"] or ["delivered"]. It does not explain the full enum state list, but the schema handles that.

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 and resource ('faxes they've sent from their Faxette account') and scopes it to a person's own sent faxes. It explicitly differentiates from the sibling 'get_fax' by naming it as the tool for a single fax's details.

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?

Gives concrete trigger examples ('what they sent last week or which faxes failed') and a clear alternative ('Use get_fax for one fax's details'). Also indicates filtering usage with the status parameter.

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