List Open Workbooks

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

The annotation readOnlyHint=true already signals a read-only operation, and the description adds useful behavioral context by specifying the return payload: a JSON list including workbook name, full path, save state, and owning Hwnd. This goes beyond the annotation to describe what the agent will receive, without contradicting the read-only hint.

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 two short sentences: the first states the action and scope, the second outlines the return fields. It is front-loaded with the core purpose and contains zero filler. Every sentence earns its place.

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 tool with no parameters and a readOnlyHint, the description is complete: it tells what it does, what it returns, and the scope. No output schema is provided, but the description lists the return fields explicitly. Nothing an agent needs to invoke it correctly is missing.

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 zero parameters, the input schema carries no semantic burden. The description implicitly defines the operation as parameterless 'list all open workbooks,' which is sufficient. The baseline for 0-parameter tools is 4, and the description meets that by making the tool's behavior self-evident.

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 states a specific verb ('List') and a specific resource ('all workbooks currently open') with a clear scope ('across every running Excel instance'). It distinguishes itself from siblings like get_workbook_info, which likely targets a single workbook, by explicitly covering all workbooks and all instances.

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 provides clear context on when to use it: when you want to enumerate all open workbooks across all Excel instances. It does not explicitly mention alternatives or exclusions, but the scope statement makes it clear this is the go-to for a global listing. A 4 is appropriate given the simplicity and the absence of parameter choices that might create ambiguity.

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