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

The description says re-sending an already-sent invoice is a harmless no-op, implying idempotent behavior. This directly contradicts the annotation idempotentHint: false. The annotation conflict makes this a serious transparency failure.

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 with no filler. The core action is front-loaded, the idempotence note is valuable, and the required parameter is mentioned last. Every sentence earns its place.

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 one-parameter tool with no output schema, the description covers the main action and the re-send behavior. However, the idempotentHint contradiction and lack of failure-mode context keep it from being fully complete.

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 0%, and the only parameter note in the description, 'invoice_id is required', merely repeats the schema's required array. It adds no meaning about what the invoice_id refers to, its format, or any constraints beyond the schema.

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?

The description states the specific operation ('Mark a draft invoice as sent'), the target resource, and the side effect ('stamps issued_at'). This distinguishes it clearly from siblings like mark_invoice_paid, void_invoice, and update_invoice.

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?

The description gives clear context: the tool is for moving a draft invoice to the sent state, and re-sending is safe. It does not explicitly name alternatives or provide when-not-to-use guidance, but the intended use case is unambiguous.

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