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

Annotations already declare readOnlyHint=true, idempotentHint=true and destructiveHint=false, so "Read-only: returns public data and changes nothing" largely restates structured data. The genuinely additive disclosure is billing behavior — 1 credit per result with a 1-credit minimum per request — which annotations cannot express and which materially affects how an agent sizes the count parameter.

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, front-loaded with the purpose, then the safety profile, then the cost model. Every clause carries information and nothing is repeated.

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 paginated, fully documented 3-parameter read tool with no output schema, the definition covers purpose, safety, billing and pagination adequately. It stops short of describing the shape of a media tweet or how cost scales with paging, which would have closed the remaining gap.

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%, and the schema already explains count (1–100, default 10), cursor pagination, and that userId is a numeric rest_id lookup-able via get-user. The description adds no parameter meaning beyond that, so 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?

States a specific verb and scoped resource: "List an X user's media tweets." The word "media" separates it from the sibling x_get_user_tweets (all tweets) and x_get_user_replies, though it never names those siblings explicitly.

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?

Usage is implied only — an agent can infer this is the media-only variant of a user timeline, but there is no explicit when-to-use, when-not-to-use, or named alternative such as x_get_user_tweets or x_search. The requirement for a numeric rest_id is delegated entirely to the schema.

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