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

Annotations already declare readOnlyHint=true, so the description goes beyond by detailing the paid tier requirement, error response (TIER_INSUFFICIENT), the computational engine (rational-method sizing, factors of safety, half-emptying time check), and the wrapping of attenuation_tank. This adds valuable context without contradicting the annotations, though it does not cover rate limits or auth steps beyond the initial check.

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 relatively long but well-organized, front-loading the critical paid-tier warning and then systematically covering the tool's standard, sizing engine, output items, and example usage. It avoids redundancy and each sentence contributes information, though it could be slightly more concise without losing clarity.

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 the tool's complexity (many parameters, nested input schema, and an output schema that is present but not shown here), the description covers the key usage context: the two ways to specify the design storm, soil characterization factors, geometry considerations, and deliverables (xlsx, dxf, pdf). It does not describe the output structure in detail, but the existence of an output schema reduces the burden. The description is mostly complete for an agent to understand how to invoke the tool 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?

With only 25% schema description coverage, the tool description provides some parameter context through example values and a brief explanation of key parameters (catchment_area_m2, rainfall_depth_mm, measured_infiltration_rate_m_per_s). However, it does not elaborate on every parameter, leaving many details to the schema's own description for the 'params' object. This partially compensates for the low coverage but not fully, resulting in a score of 3.

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?

Description clearly states the tool computes infiltration soakaways per CIRIA C753. It specifies the storage envelope types (granular-fill or modular-crate) and mentions the sizing engine. It distinguishes itself from the sibling 'compute_attenuation_tank' by noting it as a free-tier alternative, thus clarifying the tool's specific scope.

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?

The description provides explicit guidance on when to use this tool (for infiltration soakaways under CIRIA C753) and when not to, by naming the free-tier alternative 'compute_attenuation_tank'. It also includes constraints like the prohibition of VERY_HIGH hot-spot catchments without pre-treatment, and example parameters and calls that help the agent understand typical usage scenarios.

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