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

Annotations already establish read-only and idempotent behavior; the description adds meaningful context such as the fee schedule date of 8 April 2026, IHS part-year rounding, route extras like the citizenship ceremony, and the exclusion of legal fees. It consistently says this is an estimate and not advice, which is transparent about the tool's limits without contradicting the annotations.

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 compact and front-loaded: the first sentence states the core purpose, followed by a concise route list, the effective date, and scope caveats. No sentence is filler, and the length is appropriate for the tool's complexity.

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 description covers the route set, fee components, schedule date, and exclusions, which is strong for a read-only estimator. Since there is no output schema, it would be slightly improved by stating the return format or currency, but the listed components largely tell an agent what to expect.

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 route meanings, priority costs, and dependant handling. The description adds value beyond the schema by mentioning the fee schedule date, IHS adult/child rates and part-year rounding, and route-specific extras, giving the agent context about how the parameters influence the calculation.

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 opens with a specific action and object: 'Estimate the Home Office fees for a UK visa or citizenship application,' then lists the exact fee components and supported routes. This clearly distinguishes the tool from siblings like going_rate and sponsor_licence_check by scope and route coverage.

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 implies its use case through 'Estimate the Home Office fees' and the route list, but it never explicitly says when to use this tool over siblings or what to use when a route is unsupported. The 'Government fees only' and 'Information, not advice' disclaimers clarify boundaries but do not route the agent to alternatives.

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