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

The readOnlyHint already declares a safe read, so the bar is lower. The description adds the REST endpoint and single-object scope, which is useful context, but it does not disclose error behavior, rate limits, or return shape.

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, front-loaded with the operation and then the endpoint. Every phrase earns its place with no filler.

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 low-complexity, one-parameter read tool, the annotations cover safety and the schema covers the identifier. The description provides scope and endpoint, so an agent can invoke it correctly; return details and errors are omitted but less critical here.

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%, with invoice_id documented as 'Chargebee invoice id.' The description adds no syntax, format, or validation detail beyond 'by id' and the endpoint template, 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 states a specific verb 'Retrieve', a specific resource 'invoice', and the scope 'single...by id'. It distinguishes from chargebee_list_invoices by returning one record, though it does not explicitly name that sibling.

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 when-to-use guidance, no prerequisites, and no alternatives. The only cue is 'by id', which is parameter semantics rather than routing guidance for choosing between this and sibling tools.

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