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

The destructiveHint annotation already flags the operation as a mutation; the description adds the useful context that it changes accounting state and labels it WRITE. It does not say whether the change is reversible, whether already-paid invoices error out, or what permissions are needed.

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?

Three short sentences, front-loaded with the WRITE marker and the state-change warning, with zero filler. Every clause carries actionable 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 single-parameter mutation with annotations present and no output schema, the definition covers what the tool does, the side effect, and how to get the id. Missing only edge-case behavior (idempotency, error conditions) for full completeness.

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 the schema already documents invoice_id as a UUID from the matching list tool, so the description's instruction to use list_invoices largely restates it. Baseline 3 applies since the schema does the heavy lifting.

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 ('record one invoice as paid') plus the exact endpoint, which pins down the operation unambiguously. It is clearly distinguishable from the sibling list_* tools and from mark_booking_as_confirmed.

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 limoexpress_list_invoices to obtain the id before calling, which is the key prerequisite. It offers no exclusions or when-not-to-use guidance (e.g. invoices already paid, or when a payment record should be created instead), so it stops short of a full routing statement.

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