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

Goes beyond the annotations by disclosing the critical behavioral guarantees: the client cannot pay it and nothing is emailed — which is exactly the reassurance needed for a write operation that is flagged non-destructive. It also discloses the return ('Returns the new record') and the underlying POST /invoices. It stops short of warning that non-idempotent calls may create duplicate invoices.

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?

Four short sentences, front-loaded with the WRITE marker and the draft constraint, with zero filler. Every clause (draft state, no payment, no email, next-step sibling, return, endpoint) carries distinct information.

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 5-param mutation tool with no output schema, the description covers the safety profile, the return value, and the follow-up tool. The only minor gap is whether duplicate invocations create duplicate invoices, given idempotentHint=false.

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 every parameter including the clientType enum is already documented in the schema. The description only echoes the person/company distinction and adds no format, default, or validation detail beyond what the schema provides. 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 + resource + state ('create a DRAFT invoice for a person or company'), which cleanly separates it from plutio_list_invoices and plutio_add_invoice_items. The 'WRITE:' prefix and explicit draft qualifier make the operation unambiguous.

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 routes the agent to plutio_add_invoice_items for line items, establishing this as the create-then-populate first step. It does not explicitly say when not to use it (e.g. for existing invoices or subscriptions), so it stops short of full when/when-not guidance.

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