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

Goes well beyond the readOnly/destructive annotations: the file is stored out-of-band in private Storage, the signed download_url and file expire after 24h and require a fresh call, dashboards retain all branches while statements follow branch_id, and it works with read-only keys without consuming quota. These are exactly the side effects and lifecycle facts an agent needs.

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 action and artifact, then the return shape, then lifecycle and branch rules. The parenthetical enumerations are informative rather than filler, though the dense multi-clause sentences make it slightly heavier than necessary.

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 compensates by enumerating the return fields (download_url, filename, size, file_id, expires_at, structure_hash, values_hash), and it covers expiry, storage handling, branch semantics, and authorization. An agent has everything needed to call and consume the result.

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 100% and the schema already documents both model_id (key scoping/validation) and branch_id (default base branch, dashboards keep all branches). The description restates the branch behavior in essentially the same terms rather than adding new semantics, so the baseline 3 applies.

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 ('Generates the model as an Excel workbook') and immediately qualifies the artifact ('Intro + per-section sheets, native charts and dashboards, live formulas'). No sibling tool offers export, so the agent can distinguish it cleanly from read/patch/history tools.

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?

Clearly signals the context of use (exporting the model to Excel) and adds operational constraints ('a read operation, available to read-only keys, off quota') plus branch-selection guidance. It stops short of naming when-not-to-use conditions or an alternative tool, so it is clear but not fully exclusionary.

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