Open File

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

Beyond annotations, the description reveals that the opened file becomes the active document, which is a behavioral trait. No contradictions with annotations (readOnlyHint=false seems appropriate for a file open that changes active state).

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?

Three concise sentences, each serving a distinct purpose: stating the action, listing formats, and providing behavioral context plus usage alternative. No wasted words.

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?

Given the simple operation (one parameter, no output schema), the description covers all essential aspects: what it does, formats supported, behavioral effect, and alternative tool. No gaps remain.

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 sole parameter 'source' is fully described in the input schema with example values. The tool description does not add additional meaning beyond the schema, achieving a baseline score.

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 action ('open an existing image file'), the tool context ('in Photopea as a new document'), and supported formats. It distinguishes itself from the sibling 'create_document' by noting the alternative for blank canvases.

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 provides guidance on when to use this tool vs. the alternative 'create_document', helping the agent decide based on whether a blank canvas or existing file is needed.

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