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

The description discloses the key behavior beyond the annotations: 'mode=replace sets the exact list; add/remove adjust it.' This reveals that replace will entirely redefine the policy set and add/remove will incrementally modify it. That is meaningful behavioral context that annotations only hint at through the readOnly/destructive flags.

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?

Two sentences with no filler. The purpose is front-loaded and the mode clarifications follow naturally. Every word earns its place.

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 3-parameter mutation tool with complete schema descriptions and no output schema, the description is sufficiently complete. It conveys the core side-effect of replace mode and the adjust behavior for add/remove. It does not mention authorisation requirements, but the annotations cover the basic read/write/destructive profile.

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?

Although the input schema already covers all parameters, the description adds value by explaining the nuances of the mode enum: replace means exact list, while add/remove adjust it. This goes beyond the schema's generic phrase about applying policy_ids and helps an agent pick the right mode.

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 uses a specific verb and resource: 'Attach existing governance policies to the agent.' It clearly distinguishes from sibling tools like create_governance_policy and activate_governance_policy by emphasizing the policies already exist. No ambiguity in what operation is being performed.

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 makes the usage context clear by saying 'existing governance policies' and by defining the three modes: replace, add, and remove. It does not explicitly name alternatives, but the 'existing' qualifier and mode semantics tell an agent when this tool is appropriate versus creating/activating policies.

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