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

Annotations already declare readOnlyHint=false, destructiveHint=false and openWorldHint=true, and the description adds substantial context beyond them: the concrete effect (adds an approval stamp), the status transition to Approved, the verification prerequisite, that it does not pay, the confirmation-per-call behavior, and the external impact ('Reaches other people: confirm with the user before each call'). This is unusually rich behavioral disclosure for a mutation tool.

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 purpose and effect, then prerequisites, boundaries, and safety behavior. It is slightly long and includes some operational boilerplate (confirmation toggle, API key) that, while useful, dilutes the core message.

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 state-changing approval tool with no output schema, the description covers effect, prerequisite, downstream state, safety/confirmation requirements, and external visibility. An agent has everything needed to invoke it correctly.

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 both parameters are fully documented in the schema, so the description need not restate them. It adds no syntax or usage nuance for invoice_id or comment, 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 ('Approve a purchase invoice') and immediately scopes it ('in circulation'), distinguishing it from procountor_verify_purchase_invoice and procountor_approve_sales_invoice. An agent can identify the operation and its target without opening the schema.

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 clear prerequisite ('If verifiers are specified, the invoice must be verified first') and an explicit boundary ('This tool does not pay it'), which routes the agent away from payment tools. It stops short of naming the sibling tools by name, but the conditions are stated concretely.

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