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

Annotations already indicate a mutation (readOnlyHint=false). The description adds useful behavioral context: it specifies which fields can be updated and that custom claims are 'merged into the ID token and userinfo.' This goes beyond the annotations. However, the description does not disclose idempotency or the 'replaces existing claims' semantics (which the schema states), and the word 'merged' could be slightly ambiguous.

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 a single, concise sentence that front-loads the action and resource, then lists the updatable components efficiently. There is no redundant phrasing or unnecessary detail; 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 tool with 7 parameters and an existing output schema, the description covers the primary update purpose and key behaviors (field updates and claims handling). It lacks explicit usage guidance, but the schema handles parameter details and the output schema covers return values. The description is sufficiently complete for an agent to understand scope without being exhaustive.

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% and each parameter has a description. The description adds a high-level grouping (profile fields, isActive, emailVerified, custom claims) and clarifies isActive as activate/deactivate, but it does not provide per-parameter detail beyond the schema. Baseline 3 is appropriate when the schema fully documents each parameter.

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 states a clear action ('Update') on a specific resource ('mock identity') and enumerates the key fields (profile fields, isActive, emailVerified, custom claims). It distinguishes from sibling tools like identities.create or identities.delete by its focus on modifying an existing identity. The purpose is unambiguous even without explicit sibling naming.

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?

There is no guidance on when to use this tool versus alternatives. It does not mention that this is for existing identities only, nor does it contrast with identities.create or other related operations. The description is purely functional and leaves the agent to infer usage from the tool name and sibling context.

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