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

Well beyond what the annotations convey (readOnlyHint=false, destructiveHint=false, idempotentHint=true): the description discloses the token-only input contract, token staleness/expiry behavior, that existing approval requests are untouched, and that a no-op reapplication matches the idempotent hint. Minor gap: 'Requires approval-scope confirmation' is asserted without explaining what scope was confirmed or why it matters.

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?

Roughly five sentences with no filler — each contributes either a precondition, a side-effect exclusion, or the created artifact. The ordering is the weakness: the agent must read to sentence three to learn what is being created, so the core purpose is not front-loaded ahead of the procedural constraints.

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 single-parameter, non-destructive mutation with no output schema, the description covers the preconditions, the accepted input, the staleness failure mode, and the side-effect boundary, which is what an agent needs to call it correctly. It stops short of saying what a successful call returns or how rule creation failures surface, which the absence of an output schema leaves unaddressed.

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?

Only one parameter and the top-level schema coverage is effectively nil, so the description must carry the meaning — and it does, stating the token comes from preview_create_approval_rule, is the only accepted argument, and becomes invalid once the underlying records change or it expires. It does not add byte/format expectations, but the schema itself carries minLength/maxLength and the token's own description.

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?

The description names the concrete outcome — 'Prepare a rule requiring human approval for future matching invoices, with optional role chain and required decision notes' — which is a specific verb+resource, and it clearly separates this from preview_create_approval_rule and from the non-specific siblings (update_approval_rule, create_automation_rule). It is not front-loaded, though: two sentences of token mechanics precede the statement of what the tool actually creates.

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?

It names the required preceding step and the alternative explicitly: apply only the exact change from preview_create_approval_rule after user confirmation, and take a new preview if the record changed or the token expired. It also rules out expected adjacent work ('Does not notify or alter existing requests'), leaving no ambiguity about when to reach for this tool versus the preview or update variants.

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