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

With no annotations to lean on, the description carries the full burden and does so admirably: it discloses the encryption scheme (AES-256-GCM), the key model (per-account key), a critical security caveat (cloud-tier vault is Worker-decryptable, not zero-knowledge), and the destructive overwrite-on-re-put semantic. These are exactly the traits an agent needs before writing a secret.

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?

Three tight sentences, zero filler. The core operation is front-loaded, the security caveat is flagged with an explicit NOTE, and the overwrite warning closes it out. Every sentence earns its place.

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 not be described, and the remaining gaps an agent could face — encryption model, key scope, overwrite behavior, non-zero-knowledge caveat — are all covered. Nothing needed to call this tool correctly is missing.

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%, so all four parameters (name, value, hint, workspace) are already documented in the schema; the description adds only the 'keyed by name' emphasis, which aligns with the schema but contributes little beyond it. Baseline 3 is appropriate when the schema does the heavy lifting.

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 ('Store an encrypted secret ... in this account's vault') plus the keying mechanism ('keyed by name'), and the enumerated examples (API key, token, credential) pin down intent. It is clearly distinguishable from vault_get, vault_list, and vault_delete siblings.

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 the 'store a secret' framing and the overwrite note tells the agent what happens on re-put, but there is no explicit when-to-use guidance, no mention of prerequisites or auth, and no routing to sibling tools such as vault_get for retrieval or vault_delete for removal.

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