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

Annotations already declare readOnlyHint=true, destructiveHint=false and openWorldHint=false, so safety is covered. The description goes beyond them by disclosing the return-shape contract per file type and the refusal path for Excel, which materially affects how an agent plans a call. It stops short of noting size limits or truncation behavior for large files.

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 tightly packed sentences, front-loaded with the core action, then format behavior, then sourcing of the id. No filler or restatement of the name or title.

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?

With no output schema, the description still characterizes the return values by file type, and it covers the unsupported-format failure modes. Remaining gaps are edge behaviors such as binary/large-file handling and authentication expectations, but nothing essential to selecting or invoking the tool 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?

Schema coverage is 50%: mailbox is fully documented in the schema, but itemId has no schema description. The description compensates by telling the agent where the id comes from (list_onedrive_items or search_onedrive_items), which is the key missing semantic. It does not clarify id format or whether it must be a file rather than a folder.

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?

States a specific verb and resource ('Open one file and return what is in it') plus the exact file categories it handles and the formats it returns for each. It distinguishes itself from siblings by explicitly refusing Excel workbooks in favour of read_excel_range and by scoping to OneDrive files rather than the Gmail/Drive readers.

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?

Names the alternative tool (read_excel_range) and the condition that selects it, plus declares what is unsupported today (PDFs and Word documents). It also tells the agent how to obtain the required id, via list_onedrive_items or search_onedrive_items.

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