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

Annotations cover the safety profile (readOnly=false, destructive=false, non-idempotent), and the description adds substantive context beyond them: the account is created or a session established, the plan activates automatically once payment lands, and the call is free. It does not disclose failure behavior for an invalid or expired code, which for a non-idempotent account-creating call is the remaining gap.

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?

One long sentence, but the flow position and the primary action are front-loaded and every em-dash clause carries distinct information (returned address, payment branch, activation timing, cost). Slightly run-on, yet 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?

With annotations, a 100%-covered 2-param schema, and an output schema that handles return values, the description covers what the agent needs to invoke it correctly. The main omission is error handling for a bad code, which matters for a signup step but is secondary to the happy path it documents well.

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 coverage is 100% and both parameters already document the 6-digit code format and the email-matching-constraint. The description adds nothing about the parameters beyond what the schema states, so 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?

States a specific verb chain (checks emailed code, creates account or signs in) with its exact position in the flow ('Step 2 of 2') and its outputs (connection address, payment step). An agent can immediately tell this apart from start_signup, buy_plan, and check_payment.

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?

Makes the sequencing explicit ('Step 2 of 2', 'Same email used in start_signup') and notes 'Free to call', which is real guidance about cost. It does not explicitly name when to prefer buy_plan or check_payment instead, or what to do when the code fails, so it falls short of full when/when-not coverage.

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