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

Annotations already cover read-only, idempotent, non-destructive behavior. The description adds useful context beyond those annotations: the result is 'exact' and 'immutable', tied to 'Preflight v1', and the operation is 'Unmetered.' This gives an agent meaningful operational expectations without contradicting 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?

A single, tightly written sentence that front-loads the action and resource, then adds two useful qualifiers ('immutable' and 'Unmetered'). Every word earns its place and there is no redundant repetition of the schema or annotations.

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 zero parameters, an output schema, and annotations that fully describe the safety profile, the description is complete. It tells the agent exactly what will be listed, that the list is canonical and stable, and that the operation has no metering cost.

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 tool has zero parameters and an empty input schema, so the baseline is 4. The description still adds value by specifying what the output will enumerate: policy objects, canonical ruleset, and digests, which helps the agent anticipate the returned content.

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 opens with a specific verb, 'List', and names a precise resource: 'exact immutable Preflight v1 built-in policy objects, canonical ruleset, and policy digests.' This clearly distinguishes it from the sibling census tools, which concern coverage, lookups, preflight checks, and watch operations.

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 usage by identifying the exact immutable policy catalog and adds an 'Unmetered' cost signal, but it does not explicitly name alternatives or state when to prefer this tool over siblings like census_preflight or census_lookup. Usage context is present, though exclusion/alternative guidance is left implicit.

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