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

Annotations already declare readOnlyHint/idempotentHint/non-destructive, so safety is covered. The description adds that results follow plumbing code and gives the output shape (slope % and drop in cm), but says nothing about code variants, assumptions, or edge cases such as minimum diameters.

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 short sentences, the purpose and units front-loaded, no filler. The input enumeration is compact but happens to be inaccurate, which detracts slightly from otherwise tight structure.

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?

An output schema exists, so return-value detail is arguably redundant, and annotations handle the safety profile. The gap is that the description's input list contradicts the real schema, leaving an agent to reconcile 'pipe length'/'application' against fixture_type and pipe_diameter_mm.

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 schema documents both parameters at 100% coverage, so the baseline would be 3. The description actively misleads, though: it advertises inputs of 'pipe length, pipe diameter, application', but the schema has fixture_type (enum) and pipe_diameter_mm, with no length or 'application' field. That mismatch works against correct invocation.

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+resource ('Compute required drain slope') with units and the governing code, which separates it from the generic calculate_slope sibling. It does not explicitly name that sibling, so the differentiation is implicit rather than stated.

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?

'Use for plumbing or roof drainage' gives a domain context, and the description points to list_bundles for related 'plomberie' calculators. However, it never says when to pick this over calculate_slope, calculate_pipe_diameter, or calculate_pipe_flow_rate, nor lists any prerequisites.

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