Config fields lookup

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

Annotations already declare readOnly/idempotent/non-destructive, yet the description adds genuinely non-obvious behavior: exact is null when no exact match, matches falls back to 'closest field names by spelling' when nothing matches, and an error key object is returned instead of raising when the library is missing or the package is unrecognized. That error-vs-raise contract is the kind of detail an agent cannot infer from the annotations.

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?

Front-loaded with purpose, then usage, then return semantics, then error behavior — a clean progression with no filler. It does spend a sentence enumerating return fields that the output schema already covers, which is mild 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?

For a read-only lookup with an output schema and full annotation coverage, the description supplies the missing pieces: the error-object contract and the spelling-fallback behavior for matches. An agent has everything it needs to call this correctly and interpret failure modes.

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 both query and package are already documented, including case-insensitivity and word order. The description restates the exact-name-vs-words behavior but adds little syntax or constraint detail beyond the schema, so the baseline 3 applies.

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?

States a specific verb and resource ('Find a Guard config setting by name or by what it does, with type and default'), and immediately differentiates itself from validate_config and search_docs. An agent can tell exactly what this returns without opening the schema.

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 names the two alternatives and the condition that selects each ('Use validate_config instead to check a whole config you already wrote, and search_docs for prose explanations rather than field metadata'). It also states the discovery use case ('whether a setting for some behaviour exists at all').

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