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

Goes far beyond the thin annotations: the secret is never returned on any read, destinationHost is required and permanent with an https-only and allowlist constraint, changing tokenUrl on update is refused, the client secret is only sent to tokenUrl and the access token only to destinationHost. These are exactly the non-obvious behavioral constraints an agent needs before mutating state.

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?

Front-loaded with the core action and the no-return-secret rule, then per-type detail. It is dense, and the long oauthClientCredentials parenthetical is heavy to parse, but nearly every clause carries operational information rather than 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?

For a nested-object mutation tool with no output schema, the description covers the security model, permanence constraints, per-auth-type required fields, and the follow-up wiring into endpoints. Nothing critical for correct invocation 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 coverage is already 100%, so the baseline is 3; the description adds real value by enumerating which fields each auth.type consumes and by flagging optional fields (scope, audience, clientAuth) and defaults. The only shortfall is that a few semantics (e.g. what the call returns) are left implicit.

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 ('Save a new reusable credential') plus the defining mechanism ('sealed with the project's encryption key at write time'). An agent can distinguish this from update_credential and list_credentials from the description alone.

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?

Explains the intended workflow clearly: don't copy secrets, reference the entry by id via create_endpoint/update_endpoint's target.credentialVaultEntryId, and attach signingSecret credentials as senderSignature.credentialId. It stops short of explicitly contrasting create vs. update_credential, so there is a small inference gap, but practical usage is well covered.

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