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

With no annotations provided, the description carries the full disclosure burden. It names the three return artifacts and their formats, explains that sessions are hosted with callbacks, warns about the qr_text misuse trap, and calls out the Proof account authentication prerequisite. This goes well beyond what the schema alone reveals.

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-organized with clear sections: purpose/returns, agent usage, and access. Every sentence adds operational value, from the terminal-state polling hint to the authentication note. It is longer than average but not padded, and the scoping information is front-loaded.

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 tool with 6 parameters, no output schema, and no annotations, the description is remarkably complete: it covers return format, next steps, auth requirements, and lifecycle states. It does not detail error handling or channel-specific behavior, but the schema already documents the channel enum. A small gap remains around side effects like message delivery, which are implied but not explicit.

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 the baseline is 3. The description does not add parameter-level details beyond what the schema already documents, but it does contextualize some outputs (like qr_text) that relate indirectly to channel and phone_number. It neither harms nor materially enhances parameter understanding.

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 states a specific verb and resource: 'Create a new phone verification session', and immediately distinguishes it from sibling tools by naming render_auth_link and wait_for_session as downstream consumers. It also clarifies what the tool returns (deep_link, qr_code, qr_text), leaving no ambiguity about its role.

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 'Agent usage' section gives an explicit orchestration sequence: pass deep_link to render_auth_link, never render qr_text with a link renderer, and poll with wait_for_session. It also explicitly states a when-not-to-use condition: 'start_login does NOT open this tool.' This is exemplary usage guidance.

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