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

Annotations already declare the safety profile (readOnly=false, destructive=false, idempotent=false), so the bar is lower, yet the description adds real value: patch-only mutation, the fact that credit limit/hold are out of scope, and that issued documents keep their original bill-to block. 'Effects: customer record updated' is filler, and there's no mention of failure behavior for an unknown customer_id.

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?

Front-loaded with the field list, then patch semantics, then scope exclusions — a sensible ordering. The trailing 'Effects: customer record updated' restates the obvious and could be cut.

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 5-param partial-update tool with an output-schema-free interface and safety covered by annotations, the description supplies the essential semantics (patch behavior, scope boundaries, side effect on documents). Missing only edge-case handling such as unknown customer ids or validation of terms values.

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; the description adds meaning beyond it by framing the parameters as 'the customer's own facts' with a deliberate do-not-guess rule for addresses. It doesn't add format details (e.g., terms enumeration) beyond what the schema already documents.

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?

Specific verb plus resource plus the exact field set it mutates ('email, billing address, tax id, terms'). It also draws the boundary with the credit-limit and hold commands and with issued documents, so an agent can separate it from core_set_credit_limit / core_hold_customer without reading their schemas.

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?

Explains the patch contract ('only the fields you pass change') and gives an operational rule ('ask, never guess an address'), and carves out fields that belong to other commands. It stops short of naming the alternative tools explicitly (core_set_credit_limit, core_hold_customer), leaving the agent to infer which command to reach for.

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