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

Beyond the annotations (openWorldHint=true), the description discloses that the action reaches other people externally, that confirmation is on by default with a per-tool opt-out, that a portal link is inserted, and that a Cotlet API key with app access is required. These are meaningful behavioral facts an agent could not infer from the 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?

Purpose is front-loaded and sentences are information-dense, but the portal link is mentioned twice and the confirmation instruction is repeated in two consecutive sentences, which is slight redundancy.

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-shot outbound email tool with no output schema, the description covers recipient resolution, method, message default, external side effects, confirmation policy, and auth requirements. Nothing essential to calling 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 the baseline is 3. The description's statements about recipient and message defaults largely restate what the schema already documents, adding little new parameter meaning.

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 a specific verb and resource (send/email one invoice from Holded), and adds scope detail: email or post, portal link, recipient defaults. It is clearly distinguishable from siblings like holded_get_invoice or holded_add_invoice_payment.

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?

It gives concrete operating guidance: recipient defaults to the contact email, message defaults to the mailing template, and each call requires user confirmation. It does not explicitly name alternative siblings or say when not to use it, so it stops 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.