calculate_bmi

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

The description discloses the cost ($0.001 USDC via x402), which is a behavioral trait beyond what annotations provide. However, it lacks other behavioral context like output format, side effects, or whether data is sent externally, leaving the annotation-free description incomplete.

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 extremely concise with no wasted words, but it repeats the tool name ('calculate bmi') and provides minimal context. The cost detail is an efficient addition.

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?

Given no annotations, no output schema, and a simplistic input schema, this description is insufficiently complete. It fails to explain what inputs are needed, what the output looks like, or any operational details beyond cost.

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?

The input schema only exposes a generic 'params' object with no specific fields. The description does not mention height, weight, units, or any other needed parameters, so it fails to compensate for the lack of parameter-level schema.

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 clearly indicates the tool calculates BMI by using the verb 'calculate' and identifies it as a Health & Fitness tool. It distinguishes from siblings only by the explicit subject 'bmi', but it does not mention that BMI stands for Body Mass Index or that it requires height and weight.

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?

There is no guidance on when to use this tool versus alternative health-related calculators like bmr_calc or body_fat_calc. No mention of prerequisites, inputs, or scenarios for which this tool is appropriate.

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