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

Annotations already declare readOnly, idempotent, openWorld and non-destructive, so the safety profile is covered. The description adds real context beyond that: an explicit cost model (1 credit + 1 credit per returned post) and the pagination contract, which an agent needs before invoking a metered call.

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 sentences, zero waste. Purpose and cost come first, then the pagination instruction, so the most decision-relevant information is front-loaded.

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 only partially covers return values: it names meta.nextCursor but says nothing about the shape of a reply object. For a single-required-param read tool with a fully documented schema, that is a minor gap, but not a complete picture.

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 100%, and the cursor description already explains the meta.nextCursor round-trip and the 400 rejection for mismatched cursors, so the description mostly repeats it. It adds no new meaning for sort or limit, making baseline 3 the right score when the schema does the heavy lifting.

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: 'Fetch public replies to one X post.' That is enough to distinguish it from get_x_quotes or get_x_retweeters, but it never contrasts with close siblings like get_x_thread (whole conversation) or get_x_user_replies (a user's reply history), leaving overlap for an agent to resolve.

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?

Gives concrete guidance for pagination ('When meta.nextCursor is set, call again with cursor set to it'), which is genuinely operational. It says nothing, however, about when to choose this tool over get_x_thread or get_x_user_replies, so selection guidance is only implied by the resource name.

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