Warden MCP Server

Get Username

keychain_get_username

Read-only

Retrieve a login username from a Bitwarden/Vaultwarden vault using a search term or exact item ID. Ideal for fetching credentials safely when names are ambiguous.

Instructions

Get a login username matched by bw get username for a search term. Usernames are treated as non-secret scalar output, but exact item ids are safest for ambiguous names.

Input Schema

TableJSON Schema

Name	Required	Description	Default
`term`	Yes	Search term or exact item id used for bw get username.

Output Schema

TableJSON Schema

Name	Required	Description	Default
`result`	Yes

Schema Changelog

Changes observed during successful MCP inspections.

Changed2 schema fields changedv0.2.35Aug 30, 2026
- removedOutput schema / properties / result / properties / value / anyOf
```
Removed value: -[
-  {
-    "type": "string"
-  },
-  {
-    "type": "null"
-  }
-]
```
- addedOutput schema / properties / result / properties / value / type
```
Added value: +[
+  "string",
+  "null"
+]
```

Changed2 schema fields changedv0.2.19May 4, 2026

addedInput schema / properties / term / description

Added value: +"Search term or exact item id used for bw get username."

changedOutput schema / (root)

Previous value: -nullNew value: +{
+  "$schema": "http://json-schema.org/draft-07/schema#",
+  "additionalProperties": false,
+  "properties": {
+    "result": {
+      "additionalProperties": false,
+      "properties": {
+        "kind": {
+          "const": "username",
+          "type": "string"
+        },
+        "revealed": {
+          "type": "boolean"
+        },
+        "value": {
+          "anyOf": [
+            {
+              "type": "string"
+            },
+            {
+              "type": "null"
+            }
+          ]
+        }
+      },
+      "required": [
+        "kind",
+        "value",
+        "revealed"
+      ],
+      "type": "object"
+    }
+  },
+  "required": [
+    "result"
+  ],
+  "type": "object"
+}

Addedv0.1.20Mar 23, 2026

TDQS

A4.2/5.0

Behavior4/5

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

With readOnlyHint already true, the description adds meaningful behavioral context: usernames are treated as non-secret scalar output, and exact item IDs are safer for ambiguous names. This gives expectations beyond annotations. No contradiction with the read-only annotation.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Conciseness5/5

Is the description appropriately sized, front-loaded, and free of redundancy?

Two dense sentences: the first states the action and matching behavior, the second warns about ambiguity and exact IDs. No filler or repetition beyond minor overlap with the schema.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Completeness4/5

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

For a single-parameter, read-only getter with an output schema, the description is sufficient: it explains what is returned, how the term is matched, and the safest usage caveat. Explicit sibling routing would improve completeness but is not strictly required for such a simple tool.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Parameters4/5

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema coverage is 100% and the parameter description already defines 'term'. The tool description reinforces that term is a search term or exact item ID and links it to the bw get username behavior, adding retrieval semantics. It doesn't provide examples or formats, but the schema already carries the needed detail.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Purpose5/5

Does the description clearly state what the tool does and how it differs from similar tools?

The description states a specific verb and resource: 'Get a login username' matched by 'bw get username' for a search term. This clearly distinguishes it from sibling getters like keychain_get_password, keychain_get_uri, or keychain_get_notes by naming the exact field returned.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Usage Guidelines3/5

Does the description explain when to use this tool, when not to, or what alternatives exist?

The description implies the tool is used to fetch a username by search term and recommends exact item IDs for ambiguous names, but it never explicitly states when to prefer this over get_item or search_items, nor does it name any alternatives or exclusions.

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

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