list_sources

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

The annotation readOnlyHint=true already signals that this is a safe read operation. The description adds context about what is listed and that both workbooks and models are usable as `source`, but it does not disclose the output shape or possible empty results. This is acceptable but not particularly rich.

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?

A single sentence that front-loads the action and resource, then adds a clarifying explanation of scope. There is no filler, repetition, or unnecessary structure.

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 zero-parameter, read-only listing tool, this description is largely sufficient: it states what is listed and notes the explanatory component. A minor gap is the lack of any detail about the return format, but no output schema exists and the tool's behavior is simple enough that this is not critical.

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 has zero parameters and the schema has 100% coverage for an empty property set, so the description carries no parameter burden. The description still adds useful context by clarifying what the listed resources are usable as (`source`), justifying a score above the baseline.

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 names a specific action and resource: it lists open Excel workbooks and Power BI Desktop models, and explains other source forms. It is clear and specific, though it does not explicitly distinguish itself from the sibling list_data_sources, so it falls just short of a 5.

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 intended use case is implied: call this when you need to enumerate available sources and understand source form options. However, it gives no explicit when-not-to-use guidance or alternatives, especially given the similarly named sibling list_data_sources.

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