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

With readOnlyHint=true already covering the safety profile, the description adds meaningful context: the authentication prerequisite and, notably, the explicit statement that start_login will not unlock this tool, which prevents a plausible wrong-path attempt. It stops short of describing the return shape or any rate/scope limits.

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 blocks: purpose first, then a clearly labeled ACCESS note. No filler, and the actionable access constraint is easy to find.

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 read-only single-entity getter with one parameter and no output schema, the description covers what the tool returns (the user plus their verifications) and the auth gate. The only real omission is return-format/pagination nuance, which is minor here.

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% for the single required parameter, so the schema already documents external_user_id. The description only restates that the lookup is 'by external user ID' without adding format, source, or validation detail beyond the 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?

States a specific verb (Get) plus resource (single verified user and their verifications) and the lookup key (external user ID). It clearly contrasts with the plural list_verified_users sibling by being the singular fetch, though it never names that sibling to make the distinction explicit.

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?

Provides real precondition guidance: a Proof account is needed and the client must be authenticated first, and it explicitly warns that start_login does NOT open this tool. However it never tells the agent when to reach for get_verified_user versus list_verified_users or list_verifications, so the routing guidance is only partial.

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