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

Annotations already declare the mutation profile (destructiveHint=true, idempotentHint=false), so the bar is lower. The description adds substantive business rules beyond the annotations: the password/otp_secret invariant and the lead-builder-role requirement for team-shared edits or toggling sharing. It stops short of describing exactly what is overwritten on a null-vs-omitted field.

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 sentences, front-loaded with the action, then the validation invariant and the role gate. Every sentence carries distinct information with no filler, though it could be slightly tighter.

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 destructive mutation tool with eight low-coverage parameters and no output schema, the description covers the most dangerous gotchas (password/otp invariant, role gate) but omits identifier semantics and what a null versus omitted field does. Adequate but with visible gaps.

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 only 13% (only team_id is documented), so the description must compensate. It does clarify the critical password/otp_secret nullability constraint and the meaning of the shared toggle, but leaves userId, id, domain, and username semantics entirely to the schema.

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 ('Update a login by id'), which clearly distinguishes it from getCredential, createCredential, deleteCredential, and listCredentials siblings. It does not explicitly call out those alternatives, but the operation is unambiguous.

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?

Provides a real precondition ('At least one of password or otp_secret must remain set after the update') and a role gate, which implicitly tells the agent when this call will succeed. However, it offers no guidance on when to choose this over siblings or on prerequisites like first fetching the current credential.

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