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

The description adds behavioral context beyond the annotations. It explicitly mentions that custom claims are merged into the ID token and userinfo, and clarifies that isActive means activate/deactivate. It also references that claims replace existing claims (from the schema). While annotations provide readOnlyHint=false and destructiveHint=false, the description adds useful side-effect information about token/userinfo updates and activation semantics, which is valuable for an agent understanding the tool's impact.

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 core purpose ('Update a mock identity') and efficiently lists the key updateable aspects. Every word contributes value, with no filler or redundancy. It is appropriately sized for the tool's complexity and immediately orients an agent to what the tool does.

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 tool's complexity (7 parameters, nested objects, output schema present) and the annotations (all hints false), the description provides sufficient context for most use cases. It explains the primary side effects (claims merged into tokens/userinfo) and activation semantics. However, it does not explicitly mention that the identity must already exist (though implied), nor does it discuss error conditions or authorization requirements. Still, for a mock identity tool with a well-documented schema, this is a reasonably complete description, though a bit more on prerequisites would make it fully complete.

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 input schema already provides comprehensive descriptions for all 7 parameters (100% coverage), including details like 'Replaces existing claims' and 'Reserved claim names are rejected' for the claims parameter. The tool description repeats some of this (e.g., claims merged into ID token and userinfo) but does not add significant new meaning beyond what the schema already documents. Since the schema does the heavy lifting, a baseline score of 3 is appropriate.

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 the verb 'Update' and the resource 'mock identity', and enumerates the specific fields involved (profile fields, isActive, emailVerified, custom claims). This distinguishes it from sibling tools like identities.create, identities.delete, identities.get, and identities.list, which have different purposes. The description is specific and action-oriented, leaving no ambiguity about what the 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 implicitly conveys that this tool is for modifying an existing identity, as opposed to creating, deleting, or retrieving. However, it does not explicitly state when to use this tool over alternatives, nor does it provide any exclusions or prerequisites. It lacks clear guidance such as 'Use this when updating an existing identity; use identities.create to create a new one.' The usage context is implied but not explicit.

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