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

Annotations only declare readOnlyHint=true; the description adds the genuinely useful disclosure that the transport is a POST yet the operation is read-only, which prevents an agent from misreading the method as a mutation. It stops short of covering auth needs, rate limits, or pagination behavior beyond the cursor parameter.

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 tight sentences with no filler; the scope and the read-only caveat are both front-loaded. Every clause carries information the agent needs.

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?

There is no output schema, so the description carries the burden of describing what comes back, and it says nothing about the shape of the key list or how the cursor is returned. For a four-parameter paginated list tool with no annotations beyond readOnlyHint, this is adequate but incomplete.

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%, so the schema already documents apiId, limit, cursor, and externalId; baseline 3 applies. The description mirrors the externalId filter ('narrowed to a single customer') but adds no syntax, format, or defaulting detail beyond what the schema provides.

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 every key') plus its scoping constraint ('issued under one API'), which cleanly separates it from unkey_get_key (single key) and unkey_list_identities. The optional externalId narrowing is called out up front, so an agent can tell what this returns without opening the schema.

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 when to reach for this tool (you want the full key set for an API) and shows how to narrow results with externalId. However, it never names an alternative or states exclusions, so the agent is left to infer that unkey_get_key is for a single key rather than being told.

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