Upload images

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

Beyond the annotations, the description discloses valuable behavior: supported formats, a 5 MB cap, that uploads expire after a day, where the ids must be placed, and that the result carries an upload link for non-card contexts. It adds real context on top of readOnlyHint/openWorldHint. The only friction is a mild tension between 'upload' and readOnlyHint=true, though the card-mediated, ephemeral nature makes it defensible rather than a clear contradiction.

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 purpose and constraints are front-loaded effectively in the first paragraph, but the block is long and meandering. The trailing sentence listing Google Ads, Google Analytics Data, and Reddit Ads API documentation links is unrelated to uploading images and reads as boilerplate, diluting focus.

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, so return values need not be spelled out, and the description still risks little. It covers formats, size, expiration, the card mechanism, and id placement, which is enough for an agent to call a parameterless tool correctly. A brief note on what happens on failure would close the remaining gap.

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?

The tool takes zero parameters, so the baseline is 4. The description still usefully characterizes the input surface (PNG/JPEG/GIF, 5 MB limit, public-URL vs. local-file distinction), which is meaningful given there is no schema to convey any of it.

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 opening sentence gives a specific verb and resource with concrete constraints: 'upload images (PNG, JPEG, GIF up to 5 MB) for ad assets.' It also clarifies the tool's place in the pipeline by naming where the resulting ids are consumed (upload_ids of draft_image_assets, image fields of draft_reddit_ad). It stops short of an explicit 'use this instead of draft_image_assets' contrast, so it is clear but not fully sibling-differentiating.

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 gives a clear when-to-use condition: 'For images without a public URL, such as a file on the user's computer or an image attached in the chat.' It also explains the surrounding workflow (card drops files, card posts ids into chat). There is no explicit when-not-to-use or named alternative, so it is clear context without exclusions.

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