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

Adds real behavioral context beyond annotations: the result is persisted to the user's media library, the URL is returned for attachment, and it consumes one AI image action from the plan quota. Annotations already declare non-readonly, non-destructive, open-world, non-idempotent. The remaining gap is auth/pricing edge cases and whether generation is synchronous, which the direct URL-return phrasing implies but never states.

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?

The core action and output are front-loaded, with the platform-sizing parenthetical and the quota/non-posting caveats following in order of usefulness. No sentence is redundant with the name or schema.

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 supplies the return value (a media URL to attach to a post) and the side effect (stored in media, nothing published). Nothing an agent needs to call it correctly is missing for a two-parameter generation tool.

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 baseline is 3, but the description adds semantic mapping the schema lacks: the platform enum expands to concrete aspect ratios (16:9 for X/LinkedIn/YouTube, square for Instagram/Threads, 9:16 for TikTok), telling the agent exactly what the parameter controls. The prompt parameter's length bounds are left to the schema.

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 ('Generate an image for a post from a text prompt') plus scope (platform-sized, stored in user's media). An agent can distinguish it immediately from generate_video, generate_posts, and generate_persona_post without opening schemas.

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 clear context: it is for post imagery, sized per platform, and explicitly 'Nothing is posted', which scopes it away from publish/schedule tools. It stops short of naming an alternative (e.g. generate_video) or stating when-not to use it, so it is clear context without explicit routing.

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