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

Annotations already declare destructiveHint=true and idempotentHint=true, so the description's job is lighter. It still adds real value: partial-update semantics (unpassed fields are left alone), the required permission scope, and the exact endpoint. It does not spell out what 'destructive' means here (e.g. that groups replace existing membership), so a 4 rather than 5.

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?

Four compact fragments, front-loaded with the operation class, then the semantic rule, then auth, then endpoint. Nothing is redundant or padded.

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 10-parameter mutation with no output schema, the definition covers semantics, permission, and endpoint adequately. It leaves the response shape unstated and does not clarify the effect of array fields like groups, a minor gap given rich annotations.

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% with per-field descriptions, formats, and an enum, so the schema carries parameter meaning. The description only contributes the partial-update rule, which is useful but adds no field-level detail. Baseline 3 is appropriate.

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 fields of an existing customer') and adds a scope-defining clause ('only the fields you pass change') that separates it from easystore_create_customer and the get/list siblings. The 'WRITE' prefix telegraphs the operation class immediately.

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 preconditions: requires write_customers permission and targets PUT /api/3.0/customers/{id}.json. It does not explicitly name an alternative tool or state when a caller should pick a different sibling, which keeps it below a 5.

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