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

With no annotations, the description carries the behavioral disclosure burden. It meaningfully reveals assumptions: umbrella margin is £25/week, Employer NI is 15% funded from the rate, and gross pay is after employer costs. It also states that missing inputs use documented defaults. It doesn't describe the output format, but for a pure calculator this is acceptable transparency.

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 only one sentence, so it is concise, but it contains the awkward repetition 'calculator calculator' and a semicolon-separated list that is not explicitly labeled as inputs, outputs, or assumptions. It is front-loaded with the main action, but the structure is slightly muddled.

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?

The tool has five optional parameters, no output schema, and no annotations, so the description should clarify what the result is. It lists several calculation components, which partially answers this, but it never explicitly states that the tool returns an estimated take-home amount or how IR35 status affects the calculation. This is a meaningful gap.

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 description coverage is 100%, so the schema already documents each parameter and its default. The description adds a general fallback-to-defaults note and calculation assumptions, but it does not enrich individual parameter meanings beyond what the schema provides. Baseline 3 is appropriate.

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 uses the verb 'Run' and clearly identifies the resource as the 'Day rate take-home calculator', so an agent can tell this is a calculation tool. The list of components (Annual invoice value, Umbrella margin, Gross pay, Employer NI) hints at what the tool computes, though it does not explicitly state 'take-home pay'. The redundant 'calculator calculator' phrasing slightly weakens an otherwise clear purpose.

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 about when to use this tool versus alternatives like calculator_describe or submit_enquiry. The only usage-related note is that missing inputs fall back to defaults, which is about behavior rather than tool selection.

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