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

Annotations already declare readOnlyHint, idempotentHint, and destructiveHint, covering safety and idempotency. The description adds what data is returned (the full answer structure), which is useful given no output schema. It doesn't contradict annotations and adds value by enumerating the content.

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?

Two sentences, front-loaded with what the tool returns, and the usage instruction is placed at the end. No fluff, every word earns its place. Efficient and well-structured.

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 tool with one well-documented parameter and rich annotations, the description is complete. It names the return components, which compensates for the lack of an output schema. It doesn't mention potential errors, but for a simple fetch-by-slug operation, that's acceptable.

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 has 100% coverage for the slug parameter with examples, so baseline is 3. The description adds meaning by stating the slug comes from search_mtd_answers, which tells the agent where to obtain a valid parameter value. This is extra value 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 states a specific verb ('get') and resource ('one MTD answer') and enumerates the exact components returned (question, short answer, body, FAQ pairs, GOV.UK sources). It differentiates from the sibling search_mtd_answers by implying this returns a single full answer, while the sibling is for searching.

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?

Explicitly instructs the agent to 'Use the slug from search_mtd_answers', providing a direct workflow: first search, then retrieve by slug. This is a clear when-to-use directive that also implies this tool is not for searching and should be called only after obtaining a slug.

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