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

With no annotations, the description carries the behavioral burden. It discloses key behavioral traits: the result depends on operator for the independent body and on rejection_date for an actual date rather than a generic day count. It could also mention that no mutation occurs or that results are estimates, but the core conditional behavior is transparent.

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 tight sentences with no filler. The first states what the tool computes; the second gives the instructions needed to get the desired output. Every clause earns its place, and the conditional behavior is front-loaded.

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 calculator with no output schema, the description covers the required input, explains the effect of each optional input, and names the outputs the caller should expect. It does not describe return structure or example values, but it gives enough to invoke the tool correctly in all intended modes.

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 structured schema already explains notice_date, operator, and rejection_date. The description reinforces the semantics but does not add substantial meaning beyond what the schema provides, so the baseline of 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?

States a specific verb ('Work out') and a specific resource (deadlines from a private parking charge notice), then names the exact deadlines it computes: discounted amount end, operator appeal due, and independent appeal to POPLA/IAS. This clearly distinguishes it from siblings like operator_route_lookup or popla_outcomes, which have different purposes.

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?

Gives concrete guidance on which inputs to provide and why: notice date is required, operator selects the correct independent body and window, rejection date yields an actual independent-appeal date instead of a day count. It lacks explicit exclusions or references to when a sibling tool would be preferred, so it stops one step short of full routing guidance.

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