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

With no annotations supplied, the description carries real weight here: it discloses atomic all-or-nothing semantics, the required permission scopes (treasury + keys:manage), and a state precondition (revoked credentials cannot be updated). It does not state irreversibility or what happens to fields omitted from the replacement, which is the remaining gap for a mutation tool with zero annotation coverage.

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 short sentences with zero filler: the action and field scope come first, the permission and precondition follow. Nothing is repeated from the schema and nothing could be cut without losing information.

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 five-parameter destructive mutation with no annotations and no output schema, the description covers permissions, atomicity, and one precondition, but leaves the agent guessing about partial-field semantics and what the call returns. Adequate as a minimum viable definition, not complete for a full-replacement operation.

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 only 40% (name, access, and the nested walletId/array elements are undocumented), so the description has to compensate. It does so partly by enumerating the four replaceable facets and, critically, by framing the call as a replace rather than a merge, which resolves whether vaultGrants is authoritative. It never explains credentialId as the target or how optional per-grant fields behave when omitted.

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?

"Atomically replace a vault credential's name, access mode, grants, and expiry" gives a specific verb (replace, not create or revoke) plus the resource and the exact mutable fields, so an agent can separate it from create_vault_credential and revoke_vault_credential without opening a schema. It stops short of naming a sibling alternative explicitly, which keeps it out of 5 territory.

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?

"Revoked credentials cannot be updated" is a concrete when-not condition that will save a doomed call, and the field list implies the tool is for full credential reconfiguration rather than a single-field patch. What is missing is routing guidance toward alternatives (e.g. revoke_vault_credential or create_vault_credential when a credential is already revoked).

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