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

readOnlyHint=true already tells the agent this is a safe read, so the description is not carrying the full behavioral burden. It usefully adds the "metadata only" return-content constraint and the underlying API endpoint, but says nothing about pagination, result limits, or ordering for a list operation.

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 compact sentences, zero filler. The core purpose and the metadata-only constraint are front-loaded, with the API endpoint trailing as reference detail.

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 list tool with no output schema, the description conveys what is returned (metadata only) but omits any pagination or result-count behavior an agent would need to page through results. It is adequate but not complete.

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 the single parameter is fully documented in the schema, so the description adds no syntax or format meaning beyond it. The endpoint line confirms applicant_id is a query filter, which is mild added value but not substantive. Baseline 3 is appropriate.

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 gives a specific verb+resource ("List the identity documents uploaded for an applicant") and adds the scope qualifier "metadata only", which implicitly separates it from the sibling onfido_get_document that fetches a single document's detail. It does not explicitly name that alternative, so sibling differentiation is implied rather than stated.

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 parenthetical "metadata only" hints at when this list view is preferable to fetching full document details, and the required applicant_id makes the preconditions obvious. However, there is no explicit when-to-use/when-not statement or named alternative, leaving the agent to infer the choice from the noun alone.

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