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

Annotations already declare readOnlyHint, openWorldHint, idempotentHint, and destructiveHint=false, so the safety profile is covered. The description adds useful behavioral context beyond annotations: it lists the scope of manuals covered, notes that they are 'published in full,' and reveals that results include base_paths for downstream navigation.

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 longer than average due to the exhaustive tax-topic list, but that list serves the user by making the manual coverage concrete. The purpose is front-loaded, and the final sentence efficiently routes to the correct sibling tool with no filler.

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 list tool with four fully documented optional parameters and strong annotations, the description is largely complete. It explains the domain, the output's key field (base_paths), and the relationship to hmrc_manual_search. A slightly richer note on pagination or result shape would push it higher, but the schema covers paging parameters.

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 baseline of 3 applies. The description reinforces the query use case with examples like 'capital gains' and 'pensions' and mentions non-HMRC manuals, which maps to include_other_departments, but it does not add meaning beyond what the schema already documents.

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 verb-resource pair: 'List HM Revenue & Customs internal manuals and other UK departmental manuals.' It also states the key output ('see what manuals exist and their base_paths') and distinguishes itself from hmrc_manual_search by explicitly deferring section-level lookup to that sibling.

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 direct usage guidance: 'Use this to see what manuals exist and their base_paths, then hmrc_manual_search to find the section that answers a question.' This names the alternative tool and the condition that selects it, making the orchestration explicit.

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