create_session

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

Annotations only cover the safety profile (readOnlyHint=false, destructiveHint=false), yet the description adds substantial undisclosed behavior: the exact return shape, the hosted-flow-with-callbacks model, auth requirements (Proof account, PROOF_API_KEY, server restart), and the UX caveat that the user does not see tool results.

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?

Front-loaded with purpose and return values, then a clearly labeled 'Agent usage' block. Every sentence is actionable — the render_auth_link routing, the qr_text warning, the polling step, and the visibility caveat all earn their place.

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?

No output schema exists, and the description compensates by describing the return values (deep_link, qr_code, qr_text). Auth prerequisites, follow-up tools, and user-visibility behavior are all covered, so nothing needed to call it correctly is missing.

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 six parameters are already documented in the schema. The description adds workflow meaning (deep_link/qr_text are outputs, not params) but no extra syntax or constraint detail for channel, phone_number, metadata, etc. Baseline 3 is appropriate.

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 ('Create a new phone verification session') and enumerates what it returns (deep_link, qr_code, qr_text). It also distinguishes itself from siblings by noting that start_login does NOT open this tool, so an agent can route correctly.

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 explicit when-to-use steps (pass deep_link to render_auth_link, then poll with wait_for_session until verified/failed/expired) and an explicit when-not ('Never hand qr_text to a link renderer'). Alternatives and conditions are named rather than inferred.

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