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

Annotations already declare readOnlyHint, idempotentHint and openWorldHint=false, so the safety profile is covered. The description adds return-value context that matters because there is no output schema: it states that the result is the required cross-sectional area and inner diameter, with units. It does not disclose assumptions or limits of the calculation, so a 3 is appropriate.

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?

Two sentences, front-loaded with the computation and followed by the returned quantities. Nothing redundant and nothing that could be cut without losing information.

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 small, pure-calculation tool with full schema coverage, the description covers inputs and outputs adequately, which is important since no output schema exists. The one gap is the unexplained region parameter, whose effect (if any) on the computed diameter is left to the agent to guess.

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 coverage is 100% – both computational inputs (flow_m3h, velocity_ms) have ranges and units documented in the schema. The description restates those two inputs without adding syntax or formula detail. The third parameter, region (DE/CH standards), is never mentioned in the description, so its relevance to the result is unexplained.

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?

Names a specific computation (pipe diameter from volumetric flow rate and flow velocity) and even enumerates the two outputs (cross-sectional area in m², inner diameter in mm). This is far more than a restatement of the title. It loses a point only because the sibling tools are opaque identifiers, so no differentiation between tools is possible or attempted.

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?

Usage is implied rather than stated: an agent can infer this is a sizing/calculation tool from the inputs and outputs. There is no explicit guidance on when to use it, no constraints on when the result is invalid (e.g., turbulent vs. laminar assumptions), and no alternative tools named.

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