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

The annotations already declare readOnlyHint, openWorldHint, idempotentHint, and destructiveHint, establishing a safe read-only operation. The description adds behavioral context by noting the paginated nature of the response and listing included fields (slug, acronym, type, status). This goes beyond the annotations, though it doesn't cover every potential behavior like 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?

The description is concise: two sentences that front-load the main purpose, then efficiently explain return contents and usage. Every sentence provides useful information with no filler or redundancy.

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?

Given the tool's simplicity (2 optional parameters, read-only, no side effects), the description covers what users need to know: what the tool lists, what fields are included, and how the result integrates with other tools. The output schema exists, so the description doesn't need to detail all return fields. Annotations cover the safety profile, making this complete.

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?

The schema provides 100% coverage for both parameters (page and per_page), including descriptions, defaults, and constraints. The description only refers to pagination generically and adds no syntax or format details beyond what the schema already documents. Therefore, it meets the baseline for schema-covered parameters.

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 clearly states the tool's function: 'List all UK government organisations registered on GOV.UK.' It names the specific resource (organisations) and distinguishes it from siblings by noting that it can be used to 'discover slugs for use with govuk_get_organisation or govuk_search filters.' This makes the purpose unambiguous and differentiates it from related tools.

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 provides clear guidance on when to use the tool: 'Use this to browse the full government structure or discover slugs.' It also implies alternative tools (govuk_get_organisation, govuk_search) for other purposes. However, it doesn't explicitly state when not to use it, so it falls short of a perfect 5.

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