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

Annotations already declare readOnlyHint=true, openWorldHint=true, idempotentHint=true, and destructiveHint=false, indicating a safe read operation. The description adds valuable behavioral context beyond annotations: the return format ('{anchor, heading, snippet, match} hits') and the regex fallback behavior ('if it doesn't compile, falls back to literal substring'), which are not inferable from annotations alone.

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, the second explains the return format and when to use, and the third covers the regex fallback. Every sentence earns its place with no filler or repetition of schema details.

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 read-only search tool with an output schema, the description covers purpose, return format, usage guidance, fallback behavior, and relationship to sibling tools (govuk_get_section). No critical information is missing for an agent to select and invoke it correctly.

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 parameter descriptions already explain each field thoroughly. The description adds marginal value by explaining the fallback from regex to literal substring, which is partially reflected in the schema's 'Regex or literal substring' wording, but it doesn't provide significant additional semantic detail beyond the schema.

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 begins with a specific verb+resource+scope: 'Find body sections in a GOV.UK content item matching a pattern.' It also distinguishes itself from sibling tools by explicitly noting this is for content-based questions 'rather than navigating by section number,' referencing govuk_get_section as the alternative.

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 gives explicit guidance: 'Use this when answering content-based questions... rather than navigating by section number' and explains that the returned snippets help the LLM decide 'which full sections to read via govuk_get_section.' This clearly states when to use and names the alternative tool.

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