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

Adds substantial context beyond the annotations: account prerequisite, the 100 percent cap, that amount and due date become immutable (void and re-invoice instead), that the invoice is not sent, the per-call confirmation toggle, the cross-user confirmation requirement, and the API key requirement. This is exactly the behavioral disclosure an agent needs for a mutation.

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 and informative, but redundant: the percent/fixed-amount-of-total idea is stated twice, and the Progressive invoicing requirement appears twice. Sentences could be tightened without losing content.

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 mutation with no output schema, it covers prerequisites, immutability, non-delivery, and confirmation behavior, which is most of what an agent needs. It stops short of stating what the created invoice returns (e.g. an ID to use later), leaving a small gap.

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 description coverage is 100%, so parameters (amount, percent 1-100, due_in_days, job_id) are already documented in the schema. The description reinforces percent-vs-amount and due date but adds no format or syntax beyond the schema, 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 with mechanism: creating one invoice on a job for a percent or fixed amount of its total, with its own due date. This is clear and distinguishable in kind from the estimate/payment siblings, but no sibling tool is named to route the agent explicitly.

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 prerequisites (Progressive invoicing enabled, job created after that) and the constraint that total invoiced cannot exceed 100 percent. However it does not name alternatives — e.g. that a non-progress invoice or later send/void path exists — so when-to-use-vs-what is left implied.

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