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

The readOnlyHint annotation already establishes that this is a safe read, so the description's main job is to add context. It does so by listing the returned data (buyer, line items, taxes, totals, payment method, dates, IBAN, currency, PDF link) and naming the underlying API endpoint, though it omits error behavior for invalid IDs.

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 description is compact and front-loaded, first stating what is returned and then explaining the ID source. The API endpoint note is useful context but is slightly tacked on rather than integrated, keeping it just below a perfect score.

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?

There is no output schema, so the description carries the burden of explaining return contents, and it does so thoroughly by enumerating the invoice fields. With one simple parameter and its source documented, an agent has everything needed to invoke the tool correctly.

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%, and the schema already says the parameter is the invoice hash from solo_list_invoices. The description adds 'long hash' as a slight emphasis but largely repeats what the schema provides, so the baseline of 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?

The description opens with a specific verb and resource ('Get one invoice') and enumerates the returned fields, so its purpose is unmistakable. It does not explicitly distinguish itself from the sibling solo_get_invoice_status, which is the main gap keeping it from a 5.

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 tells the agent where the invoice_id comes from ('the long hash from solo_list_invoices'), which is a useful workflow prerequisite. However, it gives no explicit when-to-use versus solo_get_invoice_status or solo_list_invoices, leaving usage to be inferred from the field list.

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