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

With no annotations, the description carries the full burden and does real work: it discloses both auth requirements and a concrete failure mode (sandbox keys from self-registration get 403 until a person claims the workspace). It omits update semantics such as whether metadata is merged or replaced and what the response looks like.

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 what the tool does and how to call it, followed by the gating prerequisites. No filler or restatement of the tool name.

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 4-parameter mutation tool with a nested metadata object, no annotations and no output schema, the description covers purpose, required input shape and auth gating. The remaining gap is partial-update behavior for metadata and the return value, which matters for a nested object field.

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%, so the baseline is 3, but the description adds a constraint the schema does not encode: at least one of name, email or metadata must be supplied even though only customer_id is required. That is genuine semantic value beyond the input schema.

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 ("Change a customer") and enumerates the mutable fields, which distinguishes it from create_customer, get_customer and delete_customer without naming them. It stops short of explicitly routing the agent away from any 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?

Gives concrete invocation conditions: supply customer_id plus at least one of name, email or metadata, and it states the two prerequisites (claimed Last Price credential, claimed workspace). It does not name an alternative tool or an explicit when-not-to-use case.

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