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

Goes well beyond the annotations: clarifies that the 'sent' status does not imply actual email delivery, and discloses open-world side effects (InvoiceNow delivery via PEPPOL, IRAS reporting) that depend on stored settings. This is exactly the kind of external-effect context annotations cannot convey.

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-loads the core action and each subsequent sentence earns its place (sent semantics, prerequisite, external effects, confirmation). Dense but purposeful; no 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 destructive/open-world mutation with no output schema, the description covers the key prerequisites, state semantics, and external side effects an agent needs. It omits return/pagination details, but no output schema exists and the safety profile is already carried by annotations.

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 67% and the constrained nested object is well documented by the schema itself. The description adds the prerequisite relationship for lineItems (not a param here) but does not clarify the roles of id, companyId, or the invoice fields beyond what the schema states, so baseline 3 is appropriate.

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 state transition ('Finalize a draft invoice and mark it as sent') plus an important semantic clarification of what 'sent' means. This clearly distinguishes it from siblings like create-invoice-draft, update-invoice-draft, and preview-invoice without opening any 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 concrete prerequisite ('Requires lineItems to already be set via update-invoice-draft') and an explicit usage instruction ('Confirm the user intends to submit'). It routes the agent to the correct upstream sibling, though it doesn't explicitly state when-not to use this versus alternatives in a conditional sense.

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