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

Annotations already declare readOnlyHint=true and openWorldHint=true, so the safe-read profile is covered. The description adds a concrete cost signal ('1 credit'), which is genuinely useful context not present in structured fields, but it says nothing about behavior for private, suspended, or nonexistent handles.

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?

Two short fragments, front-loaded with the resource name, and zero filler. It stops just short of a 5 because the return-field list is comma-spliced into the first fragment rather than structured, and no verb anchors the sentence.

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?

For a single-parameter read tool with no output schema, listing the returned fields effectively substitutes for return documentation, and the credit cost is disclosed. Missing only failure-mode guidance, which is a modest gap at this complexity level.

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?

Only one parameter exists and schema description coverage is 100%, with the schema itself noting the handle may include or omit '@'. The description contributes no additional meaning about the handle parameter, so the baseline of 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 the resource (an X/Twitter profile) and enumerates the payload it returns: bio, avatar, follower/following counts, post count. That is enough to distinguish it from twitter_user_tweets or twitter_search without opening a schema, though the retrieval verb itself is left implicit.

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?

There is no when-to-use guidance, no exclusions, and no pointer to siblings like twitter_user_tweets for timeline data or instagram_profile/tiktok_profile for other networks. The agent must infer its place in a large family of profile tools.

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