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

Annotations already declare this is non-read-only, non-destructive, non-idempotent, so the write nature is known; the description usefully adds that it returns the written file path and what the output contains. It omits meaningful behavior for a file-writing tool: what happens if `path` already exists (overwrite?), whether directories are created, and the free-tier clamping is only in the schema, not the description.

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 well-formed sentence that front-loads the action and then the output shape and return value. Nothing is redundant, though the parenthetical '(excel-friendly)' and the bookkeeper clause could be tightened.

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?

No output schema exists, and the description correctly covers the return value (the file path written) and the row-level contents, which is what an agent needs to relay results. The remaining gap is side-effect behavior on an existing `path`, which matters for a file writer.

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 description coverage is 100%, including the free-tier/Pro clamping on `from`/`to` and the default-path behavior for `path`, so the schema carries parameter meaning. The description adds nothing about parameter behavior beyond noting the returned path, which is the expected 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?

States a specific verb and resource ('export the timesheet to a CSV file') plus the exact row and column shape (one row per entry with hours, billable, rate, currency, amount). It never names the nearby siblings like `report` or `invoice_summary`, so the agent must infer the distinction from the name alone.

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?

Gives a concrete intended use case — a file 'you can hand to a bookkeeper' — which tells the agent this is a human-facing file export rather than an in-chat summary. It stops short of explicit when-not conditions or naming `report`/`invoice_summary` as the alternatives.

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