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

Adds substantial behavior beyond the annotations: overwrite semantics (consistent with idempotentHint), the admin-only authorization requirement, the STS-unsupported constraint, and the fact that the secret is never echoed back. These are exactly the traits an agent needs and none are derivable from readOnly/destructive/idempotent hints alone.

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 tight sentences, each carrying distinct load: operation, authorization, input constraints, and return behavior. The mutation verb and scope are front-loaded with no filler.

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?

No output schema exists, and the description covers the return contract ('only a confirmation message', value never returned), which is the main gap an agent would otherwise face. With annotations covering the safety profile and 100% schema coverage, nothing material is missing for correct invocation.

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 value the schema lacks: it confirms all three fields are required together and constrains the kind of value acceptable for secretAccessKey (permanent IAM user key, not STS). It does not describe formats beyond what the schema's region example already provides.

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 precise verb with mutation semantics ('Store (create or overwrite)') plus the exact resource ('authenticated customer's AWS CloudWatch monitoring credentials'). The CloudWatch qualifier distinguishes it from the analogous sibling set_investigation_datadog_credentials without either schema being opened.

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 real preconditions: ADMIN only, and the credential-type constraint (use a permanent IAM user key, not temporary STS credentials, which expire and are unsupported). It does not explicitly name sibling alternatives or state when-not-to-use, so it stops short of a 5.

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