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

Annotations only declare readOnlyHint=false, openWorldHint=true and destructiveHint=false. The description adds genuinely useful context beyond those: this call issues an API key that acts on behalf of the account, which is a security-sensitive side effect the agent should know about. It does not cover failure behavior for an invalid or expired code.

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 the step marker front-loaded and the outcome stated immediately. No wasted wording, though 'Step 2' is only meaningful if the reader already knows the flow.

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?

With no output schema, the description correctly compensates by stating that the return value is an API key that acts for the account. For a two-parameter verification tool this covers the essentials; only error/expiry behavior is left unstated.

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 email and code documented in the schema, so the baseline is 3. The description restates 'code from the email' but adds no format, tolerance, or retry semantics beyond what the schema already 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: checks an emailed code and returns an API key for the account. The 'Step 2' framing signals it belongs to a multi-step flow without naming the sibling tool (start_signup) that precedes it, which is referenced only inside 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 'Step 2' label implies ordering after a signup start, but the description never names start_signup as the prerequisite or states when not to call it (e.g., existing accounts, expired codes). Usage context is implied rather than explicit.

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