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

Annotations already declare destructiveHint=true, idempotentHint=true, and openWorldHint=true, so the bar is lowered. The description reinforces the destructive nature by saying notes are 'replaced' rather than appended, but adds nothing about the 5000-character constraint, permission needs, or what happens to prior note content.

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?

Very short and front-loaded, with the operative semantics ('replace') in the first clause. It loses a point only because the title is restated verbatim as the first line, which is redundant with the tool title.

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?

An output schema exists, so return values need no explanation, and annotations cover the safety profile. What is missing is routing guidance against updateCustomer and any note about the destructive overwrite implications — enough to be usable but not complete for a mutation tool with many siblings.

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%, and both parameters (id, notes) carry their own descriptions including the 5000-character limit, so the schema does the heavy lifting. The description adds no syntax, format, or null-handling detail beyond what the schema already provides — the 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 ('Update Customer Notes') and clarifies the semantics with 'Replace the internal notes stored on a customer,' which distinguishes it from generic customer-field updates like updateCustomer. However it never names or contrasts with that sibling, so differentiation is only implied.

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?

No guidance on when to use this tool versus updateCustomer, or under what circumstances notes should be replaced at all. The only usable context is the verb 'replace,' which the agent has to infer as the selection condition.

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