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

With no annotations, the description carries the full disclosure burden. It helpfully pins down the formula lineage (Kouri 1995, factor 6.3) and the 1.80 m normalization, and referencing a public calculator supports verification, but it never states what exactly comes back (single normalized FFMI? lean mass in kg? both?) or how out-of-range body fat behaves.

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 densely packed sentence, front-loaded with the metric name and followed by inputs, normalization, citation, and a reference implementation. No filler, though the run-on construction makes the return-value intent hard to parse at a glance.

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 three-parameter pure calculator with no annotations and no output schema, the description is adequate on inputs and method but leaves the output shape ambiguous: it names 'FFMI und Magermasse' without saying whether both are returned, in what units, or whether a non-normalized FFMI is also included.

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?

All three parameters are fully described in the schema (100% coverage), so the schema already does the work and a 3 is the baseline. The description adds the conceptual mapping that these three values produce FFMI plus lean mass, but supplies no syntax, rounding, or range details beyond the 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?

States a specific computed metric (FFMI and lean mass) and the exact inputs it derives from (weight, height, body fat), plus the normalization convention and source paper. It is clearly distinguishable from siblings like bmi or koerperfett_navy, though it never explicitly contrasts itself with them.

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 statement of when to use this versus bmi, koerperfett_navy, or idealgewicht, and no mention of preconditions or valid input ranges beyond what the schema enforces. The only contextual anchor is a pointer to an external calculator for parity, which does not guide tool selection.

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