Verify eSIM login code

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

The description discloses significant behavioral context beyond annotations: 'you never see, need or handle any token' clarifies token handling, and 'do not retry a rejected code by yourself -- ask the user to re-read it, or to ask for a new one' explains failure behavior. Annotations only indicate readOnlyHint=false, but the description adds actionable safety and session management details.

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?

The description is well-structured with labeled sections (WHEN, AFTER SUCCESS, DO NOT) and every sentence delivers necessary guidance. It is concise enough to parse quickly while covering purpose, usage, and exceptions.

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?

The description is complete given the tool's complexity and the presence of an output schema. It covers the success flow ('tell the user they are signed in'), session handling, and failure handling (no automatic retries). Optional parameters (locale, currency) are adequately described in the schema, so no further detail in the description is needed.

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 100% schema description coverage, the baseline is 3. The description adds extra meaning by instructing to 'Pass that code together with the same email or phone the code was sent to,' which clarifies an important relationship between the verification_pin and email/phone parameters not stated in the schema. This elevates the score to 4.

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 clearly states the tool's function: 'verify the six-digit code the user received and open their eSIM session.' This specific verb and resource make the purpose unmistakable. It also distinguishes itself from siblings by completing the login flow initiated by request_login_otp.

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 provides a clear 'WHEN' condition: 'the user has given you a six-digit code for a login you started with request_login_otp.' It does not explicitly name an alternative tool to use instead, but the condition implies this is the correct step in the OTP flow. The 'DO NOT retry' instruction gives additional usage guidance.

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