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

Annotations already declare destructiveHint=true, idempotentHint=true and readOnlyHint=false, so the safety profile is covered. The description adds genuinely useful non-annotation context: the credential is attached only to requests for that host, never enters a sandbox, and is never returned, which explains blast radius and why no read-back occurs. It stops short of stating permission requirements or explicitly tying 'replace' to the destructive hint.

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?

Two sentences with zero filler, and the upsert behavior is front-loaded before the scoping facts. Every clause carries information the agent cannot get from the schema or annotations.

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 credential-store tool with a fully documented schema, no output schema and annotations covering mutation/idempotency, the description is nearly complete: it covers scope of attachment, secret non-exposure, and replace semantics. Missing only prerequisites (who may write credentials) and any note on rotation/verification behavior.

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 description coverage is 100% and the schema already documents host, scheme (including the bearer/basic enum semantics), secret and the conditional username. The description adds no parameter-level detail (e.g. that username is ignored under bearer), so 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 (store/replace) and resource (credential for a registry host), and the parenthetical clarifies upsert semantics so the agent knows this is not a pure create. It does not explicitly name the sibling it differs from (list_sandbox_registries, delete_sandbox_registry), leaving that differentiation to inference.

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?

Usage is implied by 'for a registry host' — the agent infers this is the way to supply credentials for host-scoped sandbox requests. However, there is no explicit when-to-use statement, no note that list_sandbox_registries should be consulted first, and no stated prerequisites for the host/scheme combination.

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