get_avatar

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

Annotations already declare readOnlyHint, idempotentHint, and destructiveHint=false, so safety is covered. The description adds a live-testing caveat, but the phrasing 'Mutation behavior has not been live-tested' is confusing for a declared read-only endpoint and does not clarify what actually happens on call. With annotations doing the heavy lifting, this is adequate but muddled.

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?

It is short and front-loaded with the endpoint identity, which is good. However, the final sentence about untested mutation behavior is boilerplate that adds confusion rather than value for a read-only GET.

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?

An output schema exists, so return values need not be explained, and the read-only annotations remove the need for extensive risk disclosure. Still, three of four parameters are undocumented and the agent is not told what the path object shape must be beyond one key, leaving meaningful holes for an endpoint tool.

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 0% and the schema exposes only generic path/query/payload/confirm_destructive objects. The description documents just one binding ('path keys: user_id'), leaving query, payload, and confirm_destructive entirely unexplained in both schema and description. For a 4-parameter tool that is a real gap.

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 names a specific verb and resource ('get_avatar: GET /v1/user/{user_id}/avatar'), so an agent knows it retrieves the avatar for a given user. No sibling tool covers avatars, so differentiation is not required. It is essentially the name plus the endpoint path, but that combination is unambiguous.

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?

'Read-only lookup' hints at the mode but does not say when to call this versus anything else, nor what preconditions exist (e.g., the user must exist, whether the avatar may be absent). There are no real alternatives among siblings, but no usage context is given either.

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