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

Annotations already declare readOnlyHint=true and openWorldHint=false, so safety is covered. The description adds genuinely useful behavior beyond that: it is a deterministic ratio-based computation (not image analysis) and returns a match percentage for every shape rather than a single label, which matters since no output schema exists.

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?

A single front-loaded sentence with the action first, followed by the input basis and the return format. No filler, no restatement of the name, every clause carries information.

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 small deterministic classifier with fully documented parameters and no output schema, the description supplies the missing return shape (per-shape match %) so the agent knows what to expect. It stops short of noting behavior for out-of-range ratios or that results are heuristic, which are minor gaps.

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%, and each parameter carries its own formula and typical range in the schema. The description only summarizes them as 'three measured outline ratios,' adding no syntax, defaults, or units beyond what the schema already provides, so the baseline of 3 applies.

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 (classify) and resource (face) and enumerates the full output space of 7 shapes plus the three input ratios, so an agent knows exactly what it produces. The only gap is that it never names or contrasts with siblings such as get_face_measurement_tool, which supplies the ratios this tool consumes.

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?

Usage is implied: the tool needs three measured ratios, which tells the agent it applies once measurements exist. However, it never states the relationship to get_face_measurement_tool (the obvious upstream step) or any when-not-to-use condition, leaving routing to inference.

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