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

Annotations already flag a non-read-only, non-destructive, open-world write, and the description usefully adds the write target (ad account image library) and the return value (image hash). It does not disclose permission/scope requirements, whether duplicates are deduplicated by hash, or any rate/size limits for fetching a public URL, which are the remaining behavioral risks.

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 tightly packed sentences with no filler; the action and return value lead, and the alternate input mode follows. Nothing is repeated from the title 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?

For a zero-required-parameter upload tool with no output schema, the description covers the essential contract: source of the image, destination library, and returned hash. The main gap is the implicit one-of requirement between image_url and media_id, which an agent could get wrong.

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 80%, so most parameters are already documented. The description adds a constraint the schema does not: image_url must be a *public* URL, and it clarifies that media_id is the chat-attachment alternative. It leaves unresolved what happens if neither image_url nor media_id is supplied, which matters given that no parameter is required.

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?

The description names a specific verb and resource ('Upload an image ... to the ad account's image library') and distinguishes itself from the sibling meta_upload_video by scope of media type. It also states the downstream artifact (image hash) that makes the tool useful.

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?

It clearly implies when to use it: before meta_create_ad, since the produced hash feeds that tool. It also contrasts the two input modes ('media_id ... Use instead of the URL'). It stops short of stating exclusions, such as when to prefer media_library or what to do if an image is already uploaded.

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