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

Annotations already declare this is a non-readonly, non-destructive, non-idempotent, closed-world mutation, and the description adds real context on top: numbers are copied rather than recomputed, expired quotes are refused by default to force price re-confirmation, and the return shape varies by whether an invoice store exists. These are exactly the behavioral traits an agent needs but cannot infer from annotations or schema.

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?

Two sentences, front-loaded with the primary action, zero filler. The branching outcome and the copied-numbers guarantee are both packed into compact clauses.

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-parameter mutation with full schema coverage and no output schema, the description covers the key unknowns: dual result paths, expiry guard, and non-recomputation. It stops short of saying what a repeated call does (idempotentHint is false) or what happens to the quote's own status afterward.

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%, so the schema already documents every parameter including the enum values and defaults. The description largely restates the 'auto' behavior already spelled out in the create_invoice schema description, adding no syntax, format, or edge-case detail beyond it.

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 ('Mark a quote accepted') plus the consequential downstream effect ('turn it into an invoice'), including both possible outcomes. An agent can distinguish this from quote_decline, quote_update, or quote_get without consulting 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 clear operational context: invoice created directly when the invoice store exists, otherwise line items are handed back, with 'never' available to only mark accepted. It does not name sibling alternatives (quote_decline, quote_update) or state when this tool should not be used, which keeps it short of a 5.

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