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

Annotations only declare readOnly=false, openWorld=true, destructive=false, but the description adds vital context the annotations cannot: the send is legally binding and cannot be recalled, it reaches third parties, it is asynchronous ('returns at once'), it requires a confirmation step by default that can be disabled, and it needs an API key with app access.

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?

Front-loads the core purpose, then the consequence, then prerequisites in a logical order. It is a bit repetitive (purpose stated twice in the first two sentences), but every remaining sentence carries an actionable constraint.

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?

With no output schema, the description still explains that the call is asynchronous and points to get_einvoice_status for the result, and covers prerequisites, irreversibility, and confirmation behavior. Nothing an agent needs to invoke 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 three parameters (invoice_id, company_id, dry_run) are already documented. The description reinforces dry_run's meaning ('run all checks without sending'), which overlaps what the schema already says, so baseline 3 is appropriate.

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 ('Send an invoice to the Sistema di Interscambio as an electronic invoice') and disambiguates from siblings like verify_einvoice, get_einvoice_status, and create_invoice by naming the delivery step and the status-check alternative. An agent can distinguish it without opening 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 operating conditions: e-invoicing must be active, dry_run runs checks without sending, and the result must be read later via get_einvoice_status. It stops short of an explicit 'use this instead of X when' contrast with verify_einvoice, so it is clear context rather than full routing logic.

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