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

Annotations establish non-read-only, non-idempotent, non-destructive behavior, and the description adds the key side effect the annotations don't convey: the previous API key stops working. It still does not explain the returned value's format or expiry.

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?

A single front-loaded sentence whose parenthetical carries the one non-obvious consequence. No filler.

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 2-parameter auth tool with no output schema, the description covers the action, inputs, and credential-invalidation effect adequately. Only the return value's nature (format/expiry of the new key) is left implicit.

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 both parameters documented, so the baseline is 3. The description adds no syntax, format, or constraint detail beyond what the schema already supplies.

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 (exchange) and resource (emailed sign-in code) and names the outcome (new API key). It is clearly distinguishable from credential-issuing siblings like partner_signin_code or partner_join.

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 phrase 'emailed sign-in code' implies this is the second step of a process begun by partner_signin_code, but it never explicitly says so or gives prerequisites. Usage is inferable rather than stated.

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