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

Annotations already declare readOnlyHint, idempotentHint, openWorldHint, and destructiveHint=false, so the safety profile is covered. The description adds genuinely non-obvious context beyond that: the $0.05 USDC x402 payment cost, which affects whether an agent should call it speculatively. It stops short of saying what happens for a nonexistent or suspended handle.

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 with no filler: the return payload is front-loaded, then use cases, then cost. The use-case list is slightly boilerplate but earns its place as routing signal.

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 correctly compensates by enumerating the returned fields, and it discloses the per-call cost. For a one-parameter read tool this is close to complete; only error/empty-result behavior for invalid handles is left unstated.

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?

There is a single required parameter with 100% schema description coverage, and the schema already explains that the @ prefix is optional. The description only says "for a handle" and adds no format, casing, or lookup-failure semantics, so the schema does all the work — the baseline 3 applies.

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?

Names a specific verb and resource ("X (Twitter) profile lookup") and enumerates exactly what is returned: display name, bio, follower/following counts, post count, website, location, creation date. This clearly separates it from interzoid_x_last_three_posts, but it never acknowledges interzoid_x_handle, which sounds closely related and would be the main sibling to disambiguate against.

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?

Lists plausible scenarios (influencer research, social listening, audience analysis, account verification), which implies when to reach for it. However, it gives no explicit when-not-to-use guidance and does not route the agent to interzoid_x_handle or interzoid_x_last_three_posts for adjacent needs.

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