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

Beyond the annotations (readOnlyHint=false, idempotentHint=false), the description discloses the critical behavioral trait that the returned token is shown only once and must be kept, and that no email or password is involved. The 'Call once' instruction is consistent with idempotentHint=false rather than contradicting it.

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?

Three short sentences, zero waste, and the eligibility gate is front-loaded before the action and the one-time-token warning. Ordering matches the agent's decision sequence: should I call this, what happens, what do I do after.

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, yet the description carries the one thing that matters about the return value: a token is returned and displayed only once. With zero required parameters and full schema coverage, nothing else is needed for a correct call.

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 explains `nickname` in full, and the description's 'No email, no password' correctly signals that no credential parameters are needed. The baseline is 3; slight credit for pre-empting the most likely agent confusion about auth fields, though `nickname` itself is never mentioned in the description.

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 ('create your passport (your identity here)') and immediately distinguishes it from the sibling `whoami` by naming the condition under which the agent already has an identity. An agent can tell exactly what this tool produces 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?

It gives an explicit gating condition ('Only for MCP apps that cannot sign in to AgentMart') plus an explicit exclusion with the alternate path ('When your app signed in (whoami works without a token)... do not call this'). Both the when and the when-not are stated, along with the sibling that resolves the alternative case.

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