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

The description goes beyond the readOnlyHint annotation by disclosing the response structure: 'focus' contains the code, 'parents' the ancestors, and 'items' the direct children. It also clearly discloses the default root-level behavior when no code is provided. This is useful behavioral context, though it does not cover error cases or year fallback behavior.

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 two sentences long and front-loads the most important information: what the tool returns and how the hierarchy is structured. The second sentence covers the special case of no code. There is no wasted wording.

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 hierarchical catalog lookup tool, the description is complete enough: it explains the main return fields, the meaning of parent and child relationships, and the root-level invocation. The optional parameters are documented in the schema, and an output schema exists, so return value details are covered elsewhere. Minor gaps like invalid-code handling are not essential for correct invocation.

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 is 3. The description adds minimal parameter meaning beyond the schema; it does reinforce that omitting 'code' returns the top level, but it adds no extra detail about 'year' or format expectations. The schema already handles the parameter semantics adequately.

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 purpose: it retrieves a PEPP code along with its parent codes and direct child codes. It also explains the root-level behavior when no code is given. However, it does not explicitly differentiate itself from pepp_search or other sibling tools, so it stops short of full sibling differentiation.

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 implies the main usage scenario: retrieve a specific code and navigate its hierarchy, or call without a code to get the top level. It provides clear context for how to invoke the tool but does not explicitly state when to prefer this tool over pepp_search or other alternatives.

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