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

The annotations already indicate this is a mutating operation that is not idempotent and not destctive, and the description adds meaningful behavior beyond that: avatar must only be set if the human chose it, and permissions are explicitly rejected. It also discloses the default_destination postcode requirement. This is strong supplementary context, though it does not detail response or side effects.

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 tight and front-loaded: the first sentence enumerates the patchable fields in one efficient list, the second gives a critical condition for avatar, and the third gives a hard exclusion about permissions. Every sentence earns its place and there is no fluff 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?

Given the high parameter count, full schema coverage, and presence of an output schema, the description is largely complete. It covers the key nuance (avatar only when human-chosen), the default_destination postcode requirement, and the permissions boundary. The only notable gap is not explicitly routing to sibling tools, but that is minor given the tool's clear patch semantics.

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 description coverage is 100%, so the schema already documents all 11 parameters well. The description adds a little extra semantic value—such as the avatar selection rule and the postcode requirement for ships-to—but mostly reiterates what the schema already says. Baseline 3 is appropriate because the schema carries the parameter documentation burden.

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 ('Patch') and names the resource (agent profile) plus the exact set of mutable fields, which makes the tool's job unambiguous. It does not explicitly name sibling tools like agent_create or agent_notify, but the scope is clear enough that it should not be confused with them.

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 implies use for updating an existing agent's profile rather than creating or authenticating, and it gives a clear exclusion: it does not accept permissions and those are handled by a human in Hub Agent settings. However, it does not explicitly say 'use agent_create to create a new agent' or provide other direct sibling routing, so usage guidance is mostly implied.

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