Set a security policy key

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

Annotations already indicate idempotency and non-read-only, so the description adds context beyond them: 'Privileged writer' and exclusivity over reserved keys. It does not contradict annotations; 'Upserts' aligns with idempotentHint. However, it stops short of explaining required auth levels or exact behavior with invalid keys, which is partly covered by the schema.

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, front-loading the core purpose and distinctiveness. Every phrase earns its place, with no filler or 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?

Given the output schema exists and annotations provide idempotency, the description covers the essential context: purpose, exclusivity, and operation type. It could mention side effects or permission requirements in more detail, but it is complete enough for an agent to select and invoke the tool correctly.

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 coverage is 100%, so the description does not need to compensate. The description's mention of 'reserved keys' and 'upserts' reinforces the schema's key/value definitions but adds no new parameter semantics beyond what 'key' and 'value' descriptions already provide.

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 it is a 'Privileged writer for reserved settings keys' and explicitly names the key prefixes (security:* / policy:*). It distinguishes from siblings by stating it's 'the ONLY tool that can write them', making the tool's purpose unmistakable.

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 explicitly provides alternatives by mentioning 'the generic data_* tools refuse reserved keys', implying when to use this tool vs those. It also labels it a 'Privileged writer' and 'Upserts one key/value', clearly conveying the use case.

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