List saved logins (no passwords)

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

Annotations already declare readOnlyHint=true, but the description adds a substantive safety guarantee the annotations don't carry: the password is NEVER returned, and password retrieval requires a separate explicit tool. It also notes the signon.rememberSignons prerequisite for new logins being persisted — real behavioral context beyond the structured fields.

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-loads what the tool returns and the no-password constraint before the routing note. Mostly tight, though 'which is a separate, explicitly named tool on purpose' is a design rationale rather than operational information and could be trimmed.

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?

There's no output schema, so describing the returned fields (origin, form action origin, username) is genuinely load-bearing. Combined with the security boundary and the pref prerequisite, an agent has what it needs; only minor items like result ordering or volume are unstated.

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 the single 'origin' parameter is already fully documented with an example. The description only says 'Filter with origin to look at one site', which adds a marginal usage hint but no syntax or format details beyond the schema. Baseline 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?

States a specific verb and resource ('List saved logins from the Firefox password manager') and enumerates the returned fields: origin, form action origin, username. It also explicitly contrasts with browser_get_login_password, so the agent can distinguish it from its closest sibling without opening either schema.

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?

Gives a concrete usage condition ('Filter with origin to look at one site') and routes the agent to browser_get_login_password when passwords are needed. It doesn't spell out exclusions for the rest of the login-management family (add_login, remove_login, fill_login), but the main alternative is covered.

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