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

Annotations only cover safety flags (readOnlyHint=false, idempotentHint=true, destructiveHint=false); the description adds real behavioral substance: the trial expands to 10 addresses and a passwordless Wozapi account is provisioned with e-mail-code login. That side effect is exactly what an agent needs before invoking a non-read-only tool.

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, front-loaded with the action, then the side effect, then the constraint. No filler and each sentence carries distinct information.

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 two-parameter mutation with no output schema, the description supplies the account-creation side effect and the user-typed-address restriction. It leaves the trial_code/API-key condition entirely to the schema, which is a minor but real gap.

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 both parameters are already documented, and the description's e-mail guidance duplicates the schema's 'Never invent one' note. Nothing new is added about trial_code syntax or the API-key case, 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?

States a specific verb and resource: 'Adds the user's own e-mail address to a trial,' plus the downstream consequence of the trial growing to 10 addresses. The action is unambiguous, though it never names a sibling (e.g. start_trial) to sharpen the boundary.

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?

Gives an explicit constraint — 'Only use an address the user typed' — which functions as a when-not rule and is repeated in the schema. It stops short of routing the agent between this tool and alternatives like start_trial or explaining when trial_code may be omitted.

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