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

Annotations already establish the safe, read-only, idempotent profile, so the bar is lower. The description adds genuine value beyond them: it names the pricing engine, the exact effect of omitting surface_area (range vs single price), and the exclusions (shipping/VAT). It still doesn't describe the response shape, but the behavioral context is solid.

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?

Three tight sentences, front-loaded with purpose and pricing tiers, then the key surface_area conditional, then scope limits. Every sentence earns its place with no filler.

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 9-parameter tool with no output schema, the description covers the pricing scope, the pivotal surface_area behavior, and exclusions. The main residual gap is the absence of any statement about the returned price structure, but it is otherwise complete enough to invoke correctly.

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 all 9 parameters. The description explains surface_area_mm2's effect, but that is largely duplicated by the schema's own description of that field, so it adds only marginal meaning. 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 ('Price a part in EUR') plus the scope (economy, standard, express) and the engine used. An agent can immediately distinguish this estimation tool from list_materials, analyze_model, and get_capabilities.

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 a clear conditional: supply surface_area_mm2 for a single price, omit it to get a range, and references analyze_model as the source for that value. It also scopes the result (excludes shipping and VAT). It does not explicitly state when to prefer this over siblings, but the conditional usage is well covered.

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