export_xlsx

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

Annotations already declare readOnlyHint=true and destructiveHint=false, but the description adds crucial behavioral context: the bytes are injected into the agent's context and cost roughly 1.4 KB of text per KB of file. This warns about significant resource consumption and explains why the sibling tool is preferred.

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?

Two sentences, front-loaded with the core purpose, followed by a concise cost/alternative explanation. Every sentence carries essential information; there is zero filler.

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 tool with no output schema, the description fully covers what the agent needs: what it returns, the cost to the agent, and when to use the sibling instead. No gaps remain.

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, so the schema leaves nothing undocumented. Per the rubric, 0 params gets a baseline of 4; the description adds no parameter-specific detail because none is needed.

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?

Description opens with a specific, unambiguous purpose: 'Return the workbook as base64-encoded .xlsx bytes.' It clearly identifies the verb, resource, and output format, and distinguishes itself from sibling save_workbook by framing this as the 'last resort' option.

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?

Explicitly states when NOT to use it ('Last resort') and names the preferred alternative: 'Prefer `save_workbook`'. It explains the key tradeoff (bytes passing through context vs. real file+link), giving the agent actionable decision criteria.

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