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

The annotations already declare readOnlyHint=true, idempotentHint=true, destructiveHint=false and openWorldHint=false, so the safety profile is fully covered structurally. The description adds only the mild qualifier 'full details,' and says nothing about behavior for a missing or inaccessible ID or whether the record is fetched live. With annotations carrying the load, a 3 is appropriate.

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?

A single front-loaded sentence with no redundant clauses or filler. It is efficient, though the terseness leaves the definition somewhat thin rather than optimally informative.

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 single-parameter getter with rich annotations and a fully documented schema, the description covers what the tool does and how it is keyed. The absence of any return-value or error context is a minor gap, partly excused by the lack of an output schema but not entirely.

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?

With one parameter at 100% schema description coverage, the schema already explains invoice_id as the ID of the invoice to retrieve. The description merely restates 'by ID' and adds no format, example, or source guidance beyond the schema, so the baseline 3 applies.

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 names a specific verb and resource ('Get the full details of a specific invoice') and scopes it to a single record by ID, so an agent can tell it apart from invoice mutations like void_invoice or send_invoice. It stops short of explicitly contrasting with any read-oriented sibling, which keeps 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?

There is no explicit when-to-use or when-not-to-use guidance, no mention of prerequisites (e.g., the invoice must exist and be accessible), and no routing to alternatives. Usage is only implied by the phrase 'by ID'.

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