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

Annotations already declare readOnlyHint=true and openWorldHint=false, so safety is covered; the description adds genuinely new behavioral context by declaring that passwords are never returned, which tells the agent what sensitive data is excluded from the payload. It stops short of describing ordering, pagination, or behavior when a project has no credentials.

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, front-loaded with what is returned and immediately followed by the data-exclusion caveat. Every clause carries information; nothing is redundant or padded.

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 one-parameter read-only tool, the description covers scope (project), returned fields, and an explicit security exclusion, while annotations cover the safety profile and no output schema exists to explain. Nothing an agent needs to invoke this 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% with a single projectId parameter documented as 'Project id (p_…)'. The description only reinforces that results are scoped to a project and adds no new syntax or format detail beyond the schema, so the baseline of 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?

The description names a specific resource ('sign-in accounts stored for a project') and enumerates what is returned (names, usernames, sites), so an agent knows exactly what it gets. It does not explicitly contrast itself with add_credential/delete_credential or other list_* tools, relying on the 'list_credentials' name and the 'stored for a project' scoping to carry that differentiation.

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: this is the tool for viewing existing credentials scoped to a project. There is no explicit statement of when to prefer it over alternatives (e.g., versus get_project or add_credential), and no prerequisites or caveats about when it returns an empty set. Adequate but leaves routing to inference.

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