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

The annotations already declare readOnlyHint=true, idempotentHint=true, openWorldHint=true, and destructiveHint=false. The description's 'Limitations: read-only' merely restates the readOnly annotation and adds no new behavioral context such as authentication requirements or rate limits.

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 short sentences with no filler; the purpose and endpoint come first and the limitation follows. Every sentence earns its place, though the read-only limitation is redundant with annotations.

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 simple read-only getter, the description covers what the tool does and the HTTP method, while annotations cover safety and the schema covers most parameters. It omits usage routing and authentication context, leaving gaps for an agent deciding between this and list_invoices.

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 83%, so the schema already documents most parameters. The description only names invoice_id and account_id as part of the path but adds no format, constraint, or interaction detail 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?

States the specific verb and resource ('Gets one invoice') and even the exact endpoint path, which distinguishes it from list/update/delete invoice siblings by singular scope. However, it does not explicitly name an alternative or sibling, so it stops short of the top score.

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?

Provides no explicit when-to-use or when-not-to-use guidance. The singular 'one invoice' implies retrieving a specific invoice, but it never mentions list_invoices or the condition for choosing this over that alternative.

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