vaultwarden_prelogin_passwordPerforms a Vaultwarden password prelogin request and returns MasterPasswordUnlockData, helping clients obtain unlock parameters needed before password verification.
Variant prelogin returning the newer MasterPasswordUnlockData shape
| Name | Required | Description | Default |
|---|---|---|---|
| form | No | ||
| params | No | ||
| json_body | No |
Changes observed during successful MCP inspections.
v0.2.2Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already provide the safety profile (readOnlyHint=false, openWorldHint=true, destructiveHint=false), and the description adds only a return-shape detail. It does not explain authentication needs, side effects, or other behavioral context beyond that hint.
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?
The description is a single short sentence with no filler, so it is concise. However, it is cryptic and does not front-load a clear action or purpose.
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?
Given three undocumented parameters, no output schema, and many sibling prelogin-related tools, the description is far too thin. It hints at return shape but leaves essential calling context 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?
The tool has three parameters (form, params, json_body) with zero schema description coverage, and the description does not mention any of them. It provides no compensating meaning for the undocumented inputs.
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?
It identifies this as a prelogin variant and mentions the return shape, giving some differentiation. But it does not state the actual operation or resource clearly, so an agent still has to infer what the tool does.
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?
There is no guidance on when to use this tool versus other prelogin or prevalidate siblings. The agent is left to guess from the name and return-shape hint alone.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.