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

Annotations only cover the safety profile (non-destructive write), while the description adds the meaningful behavioral details: the call returns an upload_id, caption acts as the post body, length limits are validated at draft-save time, and scheduling fails without a caption.

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?

Front-loads what the tool does and then the follow-up chain in three dense sentences with no filler. The long parenthetical enumeration of eleven platforms is slightly verbose but earns its place by telling the agent which platforms accept text posts.

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?

Everything an agent needs is present: what it creates, the return value (upload_id, standing in for the absent output schema), the required follow-up calls, and the caption constraint. Nothing essential is missing.

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%, so the baseline is 3; the description goes further by clarifying that the caption is shared across every platform and can be supplied later via batch_update_posts, which is semantics the schema only hints at.

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 ('Creates a text-only post (no media)') plus the return value, and distinguishes itself from media-creating siblings like create_carousel and create_video_upload by the explicit 'no media' qualifier.

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 an explicit downstream workflow: call create_post_drafts with the upload_id, batch_update_posts for per-platform captions, then batch_schedule_posts or batch_publish_now. It also names the precondition (a text post can't be scheduled/published without a caption) and lists which platforms accept text posts.

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