list_open_files

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

No annotations exist, so the description carries the burden and does so well: it discloses the empty-list case when Power BI Desktop is not running, the meaning of model_loaded=false (closed, still opening, or a dialog is open), and the consequence that every model tool will fail. It never explicitly states this is a side-effect-free read, which is the one gap given zero annotation coverage.

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?

Front-loaded with the core action, then the returned handle, then the failure-mode caveat. The parenthetical 'closed, still opening, or a dialog is open' is slightly verbose but each clause disambiguates a real state an agent would otherwise misread.

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?

An output schema exists, so return shape need not be restated, yet the description adds the one field whose meaning is non-obvious (model_loaded) and the empty-list edge case. For a zero-parameter discovery tool, nothing an agent needs to call 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?

Zero parameters, so baseline 4 applies. The description instead invests in return-value semantics (the 'instance' handle, model_loaded), which is useful but belongs to output rather than input interpretation.

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?

Specific verb and resource ('List every Power BI Desktop file currently open on this machine') with an explicit scope qualifier ('currently open') that separates it from the sibling find_pbix_files, which searches disk rather than live instances. The second clause names its downstream role — supplying the 'instance' identifier the other model tools need.

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?

Implied clearly as the entry point of the model-tool workflow ('the identifier to pass to the other model tools'), and it gives an actionable branch: if model_loaded is false, ask the user to open the file. It does not explicitly contrast with find_pbix_files or state prerequisites, so it falls short of full when/when-not guidance.

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