upload_image

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

With no annotations provided, the description carries the full burden of behavioral disclosure. It mentions the return value (hosted image URL) but doesn't cover important aspects like authentication requirements, rate limits, file size restrictions, supported image formats, or error conditions. For a mutation tool with zero annotation coverage, this leaves significant gaps.

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 description is extremely concise with just two sentences that each serve distinct purposes: the first explains the upload action and destination, the second specifies the return value. There's zero wasted language and it's perfectly front-loaded.

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 single-parameter mutation tool with no annotations and no output schema, the description provides basic purpose and return value information but lacks important context about behavioral traits, error handling, and usage guidelines. It's minimally adequate but has clear gaps that could affect agent decision-making.

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 description coverage is 100%, so the input schema already fully documents the single parameter. The description doesn't add any additional parameter semantics beyond what's in the schema, maintaining the baseline score of 3 for when the schema does the heavy lifting.

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 specific action ('Upload'), resource ('base64-encoded image'), and destination ('Substack's CDN'), distinguishing it from sibling tools that handle drafts, posts, notes, and subscribers. It provides a complete purpose statement with no ambiguity.

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?

The description offers no guidance on when to use this tool versus alternatives or any prerequisites. While it's clear this is for uploading images, there's no mention of when this is appropriate compared to other content creation tools like create_draft or create_note.

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