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

Annotations already declare it is not read-only, not open-world, non-idempotent, and non-destructive, but the description adds substantial context: the phone-camera measurement, on-device privacy, one-hour link lifetime, three-watch limit, and what Send shares. Nothing contradicts the annotations.

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 dense but front-loads the user need and then explains the flow, privacy, limits, and image handling. It is somewhat verbose and repeats schema-covered details, but every sentence contributes operational context.

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 complex start-session tool with no output schema, the description covers the lifecycle, phone handoff, privacy, expiry, watch limit, image inputs, and result retrieval through get_try_on_result. An agent has enough context to call it correctly and set expectations.

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 schema already documents watches, photos, image_url, and sizing fields in detail. The description reinforces the image_url versus photos distinction and the three-watch limit, but adds little syntax or semantics beyond the rich schema, so 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?

The description states a specific action: it creates a QR link that opens on the phone, measures the wrist, and lets the person try on watches at true size. It references get_try_on_result for the result, but does not explicitly differentiate from siblings like fit_watch or suggest_sizes, so sibling differentiation is partial.

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?

It gives a clear use case: for someone who does not know their wrist size or wants to see watches on their own wrist. It implies the flow into get_try_on_result, but does not state when to choose this over fit_watch or suggest_sizes.

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