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

readOnlyHint=false signals a state-changing operation, and the description goes beyond that by disclosing the email side effect, 6-digit code and 15-minute validity, the human/operator dependency, and the identical response whether or not an account exists. It does not cover rate limits or whether previous codes are invalidated, but the key behavioral traits are well communicated.

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?

Every sentence carries useful information: workflow position, side effect, code expiry, human step, next tool call, auth requirement, and response invariance. The description is front-loaded with purpose and remains readable despite covering several distinct facts.

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 single-parameter tool with no output schema, the description covers purpose, workflow, auth, side effects, and response invariance. The only notable gap is that it never specifies the actual response body or status shape, which an agent may need in the absence of an output schema.

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?

The schema already fully documents 'email' with type, maxLength, and a privacy note at 100% coverage. The description reinforces that the email belongs to the account owner and adds that no credentials are needed, but it does not need to compensate for missing schema information.

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?

The description opens with 'Step 1 of joining Matrix' and clearly states the action ('Sends a 6-digit verification code') and target ('email of the account owner'). It differentiates this tool from the follow-up register_agent by naming the next step, so an agent can place it within the workflow.

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 description positions the tool in a clear sequence: use it first, then call register_agent with the email and verificationCode. It also notes that no credentials are required, which helps an agent decide when this is appropriate. It does not explicitly name alternatives or state when not to use it, but the workflow context is sufficient.

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