x_post

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

Annotations already declare the read-only, idempotent, non-destructive profile, so the bar is lower, yet the description adds real traits beyond them: it reports missing IDs rather than failing, explicitly does not expand full reply threads, and discloses per-returned-post billing. That cost and missing-ID behavior are genuinely useful and not inferable from the annotations.

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 core action and progressively adding scope, exclusion, and cost. No sentence is redundant and nothing is buried.

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 usefully characterizes the response (includes quotes and reply references, reports missing IDs). Cost and scope limits are covered. It is only slightly incomplete in not describing the compact/full detail tradeoff at a level beyond the schema's own text.

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 50%: the detail enum is self-documented in the schema, while ids has no schema description beyond its numeric pattern. The description says 'numeric ID' but adds no meaning about batch size, format, or what compact vs full actually returns, so it does not compensate for the coverage gap. 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 (Read) and resource (X posts) with the exact lookup key (numeric ID) and even names the data provider (TwitterAPI.io). The 'by numeric ID' qualifier cleanly separates it from the sibling x_search, which is for discovery rather than direct ID retrieval.

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 'by numeric ID' framing clearly implies the precondition (you already have post IDs), and 'does not fetch a full reply thread' is an explicit scope exclusion that prevents misuse. It stops short of naming x_search as the alternative for ID discovery, so it isn't a full when/when-not routing statement.

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