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

Adds real context beyond the annotations: a rate limit of 3 verification messages per hour, and the side effect that webhook and Widely chat channels are re-checked with a test message. It does not say whether previously issued codes are invalidated or what happens on hitting the rate limit, which keeps it from a 5.

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, purpose first, then the trigger condition, then the side effect and rate limit. No filler, though the middle sentence about webhook/Widely re-checking is slightly compressed and takes a re-read to parse.

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?

Complete enough for a one-parameter mutation with no output schema: the trigger, side effects, and rate constraint are all disclosed, and annotations cover the safety profile. Return behavior (e.g., what the resend response contains) is left implicit, which is the only remaining 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?

With a single parameter at 100% schema description coverage, the schema already carries the semantics. The description only implies that the id refers to a callback channel, which is a marginal addition over the schema's 'Callback channel id.' 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 ('Sends a fresh verification code for an ... callback channel') and scopes the channel types covered (email, SMS, WhatsApp, webhook/Widely chat). This is clearly distinguishable from the sibling verify_callback_channel, which consumes rather than issues the code.

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 trigger condition: use when verify_callback_channel returns code_expired or code_locked, naming the alternative tool and the exact post-condition that selects this one. That is about as close to a routing rule as a description can get.

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