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

Annotations already declare readOnlyHint=false, destructiveHint=false, openWorldHint=true. The description adds genuinely new behavioral context beyond them: nothing is delivered to the client, the tool auto-executes without prompting, and it requires the user's Cotlet API key with access to this app. These are exactly the kinds of side-effect and auth facts an agent needs for a non-read operation.

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?

The key facts are front-loaded, but the same idea is stated three times in different words ('Not sent until you send it,' 'The client gets nothing until send_invoice runs,' 'It reaches no one'), which is redundant padding for a definition this length.

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 tool with no output schema, the description covers the effect (draft only), the return shape (invoice_id and total), the auth requirement, and the non-notification behavior. Nothing an agent needs to call it correctly is missing.

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 all three parameters (contact_id, items, due_date) are already documented in the schema. The description restates that the invoice is built from line items for one contact but adds no syntax or format detail. Baseline 3 applies when 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 (creates a draft invoice), the scope (one contact, from line items), and implicitly contrasts with send_invoice, which is named. An agent can distinguish this from pixieset_send_invoice without opening either 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?

Explicitly says the invoice is 'Not sent until you send it' and 'The client gets nothing until send_invoice runs,' naming the alternative tool and the condition that selects it. It also states that this variant needs no confirmation ('it runs without asking').

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