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

Annotations already cover readOnly/idempotent/non-destructive, so the description only needs to add what they don't say — and it does, by declaring the corpus is fixed at 26 codes, the call is tiny and one-shot, and the payload duplicates hints already embedded in diagnostics. No return-shape detail, but an output schema exists to carry that.

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?

Three short sentences, front-loaded with the usage trigger and closing on the differentiation from inline hints. Mild redundancy between "Tiny one-shot call" and "just gives you the canonical list up front," but nothing that wastes real space.

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 zero-parameter, read-only lookup with an output schema and full annotation coverage, the description covers what it returns (26 codes and hint templates) and why it exists (pre-populating retry strategies). Only the static/versioned nature of the catalogue is left unstated, which is minor.

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?

Zero parameters; the schema is empty and there is nothing to disambiguate. The description's note that it is a "one-shot call" reinforces that no arguments are needed, which is the right level of detail here.

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 names a specific resource: the kernelCAD 26-code diagnostic catalogue plus hint templates. It is clearly distinguished from the other lookup_* siblings by scope (codes, not API/cookbook/skills), though it never names those siblings explicitly.

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?

"Use this when you need..." sets the trigger, and "Hints are also inline on every emitted diagnostic — this tool just gives you the canonical list up front" supplies an implicit when-not: don't call it just to interpret a single diagnostic you already have. It stops short of naming a concrete alternative tool such as why_did_this_fail.

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