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

Annotations mark it non-read-only, open-world, non-idempotent and non-destructive; the description adds value beyond that with supported formats (JPEG/PNG/GIF/WebP), an 8MB size cap, the data: prefix acceptance, and the signed-URL staleness failure mode.

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?

Dense but disciplined: purpose and return value first, then the mutually exclusive inputs with their constraint, then the preference rationale, then downstream usage. Every sentence carries information an agent needs.

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?

An output schema exists, yet the description still explains the key return (image_hash) and how to consume it in create_meta_link_ad / create_meta_video_ad / create_meta_carousel_ad. For a 4-param upload tool, nothing material 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 0%, so the description must carry the load, and it does: object_story_id is tied to an existing Page post (id from list_meta_page_posts), image_url is a public link, and image_base64 is the file itself. account_id is left unexplained, which is the only gap.

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 (uploads an image creative to Meta) and names the concrete artifact produced (image_hash) with its reuse scope. It is clearly distinguishable from siblings such as upload_image, upload_tiktok_image, and upload_meta_video.

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?

Explicitly states 'Give ONE of' the three source inputs and then gives a preference rule with rationale: prefer object_story_id for a post's own image because Facebook CDN links are signed and short-lived and can 403. It also names the downstream tools to use the hash with.

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