Shared preference catalog

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

Annotations already include readOnlyHint=true, and the description reinforces this with 'Read-only'. Beyond the annotation, it adds valuable context: the tool is engine-owned, it describes existing preferences rather than reading effective values, and it lists the fields included. This gives the agent a clear behavioral model without redundancy.

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 and every word earns its place: it states the resource, its contents, its consumer, the alternative for effective values, and its read-only nature. No filler or repetition.

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 catalog tool with an output schema, this description is fully complete. It explains the tool's purpose, ownership, field structure, and relationship to oma.pref(), while the output schema covers return format. Nothing important is missing.

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 the input schema confirms this (empty properties). The description adds no parameter information needed. Baseline for 0 params is 4, which is appropriate since there is nothing to document.

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 identifies this as a catalog of shared preferences, with a specific verb ('describes') and precise scope (key, type, label, default, options). It distinguishes itself from siblings by explicitly noting it 'only describes what exists' and that it is engine-owned, which no other sibling tool does.

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 provides clear usage context: it is the catalog the settings app renders, and it explicitly tells when not to use it ('Apps read effective values via oma.pref(); this tool only describes what exists'). It does not name an alternative sibling tool, but the oma.pref() reference serves as a functional alternative.

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