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

Annotations already declare readOnlyHint=true and destructiveHint=false, so the safety profile is established. The description adds the scope of 'a single customer' and the lookup-by-Id behavior, but it doesn't disclose any additional behavioral traits (e.g., what happens if the Id doesn't exist, whether it returns deleted customers, or response shape). With annotations carrying most of the burden, 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?

The description is one concise sentence that completely covers the core purpose. There is zero wasted text and the essential scope ('single customer', 'by Id') is front-loaded.

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-by-Id tool with two well-documented parameters and annotations declaring it safe, the description plus schema is nearly complete. The only missing context is clarification of edge-case behavior (e.g., not found, error handling) or how 'company' behaves when multiple are connected, but the schema already covers the connection ambiguity. This is complete for practical invocation.

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 coverage is 100%, with the 'id' parameter documented as 'QuickBooks Id of the Customer' and 'company' documented clearly. The description adds no new parameter semantics beyond restating 'by Id'. Baseline 3 is correct when the schema does the heavy lifting.

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 ('Get'), a specific resource ('a single customer'), and the system ('QuickBooks Online'), and identifies the lookup key ('by Id'). This clearly distinguishes it from broader tools like search_customers or list-like tools, and from customer-related aggregate tools like get_customer_balance or get_customer_sales.

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?

The description clearly implies the tool is for retrieving a specific customer when the Id is known, which is a clear context. It doesn't explicitly name alternatives (e.g., search_customers for finding by name) or state exclusions, so it misses the explicit 'when not to use' guidance, but the context is clear enough for an agent to select it for id-based lookups.

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