upload_image

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

The description covers the basic operation and output but lacks details on error handling, allowed image formats, rate limits, or authentication requirements. Given the absence of annotations, the description carries the full burden but only provides minimal behavioral context.

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 sentences, no wasted words, front-loaded with verb and resource. Perfectly concise.

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 simple upload tool with one parameter, the description is fairly complete: it explains the input format and the return value. However, it lacks mention of potential errors, size limits, or supported image types, which could affect usability.

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?

With 100% schema description coverage, the baseline is 3. The description does not add additional meaning beyond what the input schema already provides for the single parameter.

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 clearly states the tool uploads a base64-encoded image to Substack's CDN and returns the hosted URL. It uses a specific verb+resource structure and distinguishes itself from siblings which focus on drafts, notes, and posts.

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?

No explicit guidance on when to use this tool versus alternatives. While the purpose is clear, there is no mention of prerequisites, file size limits, or when alternative tools might be more appropriate.

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