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

Annotations already cover the safety profile (readOnlyHint=true, destructiveHint=false, openWorldHint=false), so the bar is lower. The description still adds real value by scoping the response to public fields and naming excluded ones (email, stripeCustomerId, billing), which is information annotations cannot convey. It stops short of describing not-found behavior or pagination/error handling.

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?

Three short sentences, zero filler, with the core action and the return-scope caveat front-loaded. Every sentence carries distinct information.

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?

With no output schema, the description steps in by enumerating the fields that are and are not returned, which is the main thing an agent needs. Minor gaps remain: no guidance on precedence when both identifiers are passed, and no statement about missing-user behavior.

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 both parameters are already fully documented, including the usernames/{handle} resolution the description repeats. The description adds no precedence rule for when both optional identifiers are supplied, so it sits at the baseline.

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?

States a specific verb and resource ('Get one public profile') plus the two accepted identifiers, which cleanly separates it from sibling lookup tools like search_users, discover_users, and whoami. An agent can tell what it returns without opening the schema.

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 phrase 'one public profile by username or userId' implies the single-record lookup case, providing context that contrasts with the plural/search siblings. It does not, however, explicitly name search_users or discover_users as the alternative, nor say when this tool is the wrong choice.

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