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

readOnlyHint=true already covers the safety profile, so the bar is lower. The description adds non-obvious context beyond annotations: a Proof account is required, the failure mode is re-authentication via the client (/mcp → Authenticate), and that start_login is not a valid remediation path. It does not mention pagination behavior or result size, but the output schema covers the response shape.

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 the purpose in the first sentence and the auth constraint second, with no filler. The only slightly redundant clause is 'then call this tool again', which restates the retry implied by the error condition.

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?

Output schema exists, so return values need not be explained, and the parameters are fully documented in schema. The auth prerequisite — the one thing that would otherwise cause a hard failure — is covered explicitly, leaving only minor gaps around pagination defaults.

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 optional parameters (page, limit) are documented with bounds in the schema itself. The description says nothing about paging or default ordering, so it adds no meaning beyond the structured fields — the baseline 3 applies.

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 ('List verified users') plus a meaningful grouping semantic ('grouped by external_user_id', 'all verifications per user') that distinguishes the result shape from get_verified_user. It does not explicitly name the nearest siblings (list_verifications, get_verified_user), so an agent must infer the boundary from the grouping detail.

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 ACCESS block gives real usage guidance at the authentication layer, including an explicit exclusion: 'start_login does NOT open this tool', which saves an agent a wrong turn. However, there is no guidance on when to choose this over list_verifications, list_revoked_proofs, or get_verified_user, so the core routing decision is left implied.

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