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

Annotations already cover the safety profile (readOnly, non-destructive, closed-world), and the description adds meaningful context beyond that: it is stateless (no persistence or mutation side effects) and it returns not just one number but a breakdown plus p25/p75 scenarios. With no output schema, disclosing those return semantics is genuinely useful, though edge cases (e.g. how copay interacts with coinsurance, ordering of deductible/OOP application) are left unstated.

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 core purpose and scoping label before the usage note. No filler; each sentence contributes either the what or the when.

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 an 8-parameter tool with no output schema, the description adequately covers inputs, outputs, and the stateless nature, and the schema carries the parameter detail. What is missing is how the p25/p75 scenarios are derived and how optional fields like copay or oop_met change the result, which would help an agent set expectations.

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 all 8 parameters, including optional copay, oop_met, deductible_met, and preventive_exception, are already documented in the schema. The description restates the required inputs (deductible, coinsurance, OOP max) but adds no extra meaning such as interaction rules or units beyond what the schema provides, so the baseline 3 applies.

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 names a specific verb and resource ('Stateless insurance math', 'calculate liability') and states exactly what it returns: patient responsibility, plan payment, the breakdown, and p25/p75 scenarios. It implicitly separates itself from sibling estimate tools by scoping to inputs you already have, but it never names an alternative like full_estimate or estimate_procedure_cost, so the differentiation is inference-based rather than explicit.

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 when you already have a dollar amount (e.g. from an EOB or a prior estimate)' gives a clear precondition that tells the agent when this tool applies versus one that generates an estimate from scratch. There is no explicit when-not guidance or named alternative, which keeps it short of a 5.

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