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

Annotations already cover safety (readOnlyHint=true, destructiveHint=false, openWorldHint=true), and the description adds genuinely useful context beyond them: sensitive fields (card numbers, passwords) are never returned, which affects how the agent should treat and trust the payload. It stops short of stating not-found or error behavior.

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 sentences, front-loaded with the resource and its field contents. The trailing 'GetCustomerById' is a redundant restatement that adds no information, but the rest is tight with no other waste.

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, the description correctly compensates by enumerating what the record contains (contact, address, credit status and limit, balance, billing settings) and what is excluded. For a one-parameter read tool it is nearly complete; only error/not-found behavior is unaddressed.

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% and the single parameter is documented as 'Internal customer id.' The description repeats essentially the same framing, adding no format, range, or lookup-origin detail beyond the schema, so 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?

States a specific verb and resource ('The full customer record by internal customer id') and even enumerates the returned fields, so an agent knows exactly what it gets. The 'internal customer id' qualifier implicitly separates it from the phone/code lookup siblings, though it never names them.

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?

Usage is only implied: the 'internal customer id' phrasing hints that this is the id-based path rather than the code- or phone-based lookups in the sibling set. There is no explicit when-to-use, no exclusion, and no mention of prerequisites such as needing a known internal id.

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