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

Annotations already declare readOnlyHint=true, but the description adds genuinely useful context by flagging that the tool is 'Read-only despite being a POST' — resolving an apparent contradiction an agent might otherwise infer from HTTP-method conventions. It gives no pagination or result-volume behavior, but that is largely covered by the schema.

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 short sentences with zero waste; the core purpose and the critical read-only caveat are both front-loaded. Nothing is repeated from the title or annotations verbatim.

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 3-param, zero-required list tool with full schema coverage, readOnlyHint annotations, and no output schema, the description covers purpose and the POST/read-only quirk adequately. It could say more about pagination flow (cursor round-tripping), but that is documented in the schema.

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%, with limit (1-100), cursor, and search all documented in the schema. The description adds no parameter-level meaning beyond that, so 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?

The description names a specific verb and resource ('List identities') and even clarifies what an identity is ('the end users or organisations your keys belong to') plus the underlying endpoint. It does not explicitly distinguish itself from unkey_get_identity or unkey_create_identity, relying on the verb to do that work, so it falls short of the sibling-differentiating bar.

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?

Usage is only implied: listing implies enumeration, and the read-only note implies safe retrieval. There is no statement of when to pick this over unkey_get_identity (single lookup) or unkey_list_permissions, nor any exclusion or prerequisite guidance.

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