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

'Read-only; changes nothing' merely restates readOnlyHint=true and destructiveHint=false, earning no credit against the annotation bar. The only novel claim, 'Money is integer minor units (cents)', is irrelevant to a tool whose schema contains no monetary fields, so it adds no useful behavioral context and risks confusing the agent.

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?

Three short sentences, front-loaded with the purpose, which is good structure. However, the final sentence about money units is wasted text for this tool, so one of three sentences does not earn its place.

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?

With no output schema and zero required parameters, the description should clarify what is returned (single customer vs. list, partial-match behavior) and that at least one of name/email is expected. It covers neither, and the irrelevant money note dilutes what little guidance is present.

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 only 50%: the 'name' parameter is documented but 'email' has no description in either schema or description. The description adds no parameter meaning at all (its money note maps to nothing), so it fails to compensate for the coverage gap.

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 a specific verb and resource ('Look a customer up'), which is clearly distinguishable from write-oriented siblings like customers_create and customers_delete. It does not, however, explicitly differentiate itself from adjacent reads such as orders_lookup, so it stops short of 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, when-not-to-use, or alternative routing. The only implicit guidance comes from the name parameter's note about using a name 'when the email is not to hand', which hints at lookup modes but is buried in the schema rather than the description.

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