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

Annotations already supply readOnlyHint, idempotentHint and destructiveHint=false, so the bar is lower; the description still adds real value by naming the two failure flags and, importantly, warning that plan names, inclusions and agent name come back under 'untrusted_user_content' — a security-relevant provenance cue not expressed in any structured field. 'Nothing is booked or recorded' reinforces the read-only profile. It does not say whether fees are live or cached, nor any rate limits.

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?

Purpose is front-loaded and every clause carries information: plan breakdown, failure flags, sibling fallback, untrusted-content warning, side-effect disclaimer. It is a dense single sentence that would read faster split into two, but nothing is wasted.

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?

With no output schema, the description takes on the burden of describing return shape and does so — per-plan cost breakdown, the two boolean flags, and where untrusted strings live. For a two-parameter read-only lookup, an agent has everything needed to call it and interpret both success and failure responses.

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%, so both parameters are already documented with examples and ranges. The description restates that they are a UK postcode and an estimated sale price without adding format, tolerance or rounding guidance beyond the schema — baseline 3 applies when the schema does the heavy lifting.

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-like retrieval ('selling fee plans available from the local agent'), the two scoping inputs (UK postcode, estimated sale price) and exactly what each plan contains (up-front, on-completion, total, no-sale cost). The added note that request_valuation still works in both failure cases implicitly separates this tool from the sibling it most resembles.

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 clear context for use (selling fee plans for a postcode and price) and tells the agent what to do when the tool cannot help — available:false means fee plans are not offered online, covered:false means no agent covers the postcode, and request_valuation remains valid in both. It does not explicitly contrast with get_landlord_fees for rental fee enquiries, which is the nearest confusable sibling.

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