Mixer4AI

Register Agent Card

register_agent_card

Registers a new agent card - and, if x-mixer4ai.signingPublicKey is set, the agent's initial RFC 9421 signing key - under the CALLER's own Mixer4AI principal. Requires a sponsor's Entra bearer token (Authorization: Bearer ). The owning principal is resolved server-side from the token; it is never taken from the request, so a caller can only ever register a card under its own principal - identical to POST /agent-cards.

Tool call template

Replace each placeholder with a value matching the input schema. Only required parameters are included; add optional parameters as needed.

{
  "id": 1,
  "jsonrpc": "2.0",
  "method": "tools/call",
  "params": {
    "arguments": {
      "request": "<request>"
    },
    "name": "register_agent_card"
  }
}

Input Schema

Name	Required	Description	Default
`request`	Yes	The agent card to register: an A2A-compatible manifest carrying the x-mixer4ai vendor extension. Set x-mixer4ai.signingPublicKey (base64 SubjectPublicKeyInfo of a NIST P-256 public key) to register the agent's initial signing key at the same time.

Schema Changelog

Changes observed during successful MCP inspections.

Changed1 schema field changedSep 14, 2026
- addedInput schema / properties / request / properties / x-mixer4ai / properties / reputationScoreBreakdown / properties / incorporationContinuityLine
```
Added value: +{
+  "default": null,
+  "type": [
+    "string",
+    "null"
+  ]
+}
```

Changed1 schema field changedAug 7, 2026

addedInput schema / properties / request / properties / x-mixer4ai / properties / reputationScoreBreakdown

Added value: +{
+  "default": null,
+  "properties": {
+    "asOf": {
+      "format": "date-time",
+      "type": "string"
+    },
+    "baseline": {
+      "type": "number"
+    },
+    "components": {
+      "items": {
+        "properties": {
+          "contribution": {
+            "type": "number"
+          },
+          "eventCount": {
+            "type": "integer"
+          },
+          "eventType": {
+            "type": "string"
+          }
+        },
+        "required": [
+          "eventType",
+          "eventCount",
+          "contribution"
+        ],
+        "type": "object"
+      },
+      "type": "array"
+    },
+    "formulaVersion": {
+      "type": "integer"
+    },
+    "score": {
+      "type": "number"
+    }
+  },
+  "required": [
+    "score",
+    "baseline",
+    "formulaVersion",
+    "asOf",
+    "components"
+  ],
+  "type": [
+    "object",
+    "null"
+  ]
+}

First observedJul 27, 2026

TDQS

A3.6/5.0

Behavior4/5

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

Annotations already declare readOnly=false, idempotent=false, destructive=false, openWorld=false, and the description adds genuinely non-obvious behavior: the principal is resolved server-side from the token and never from the request, so cross-principal registration is impossible. With idempotentHint=false it would help to say what happens on a duplicate registration, and whether the card lands live or pending approval given the self-registration siblings.

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

Conciseness4/5

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

Three tight sentences with the core action and the signing-key conditional front-loaded, then the auth requirement, then the ownership guarantee. No filler; the closing REST endpoint comparison earns its place only marginally.

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

Completeness3/5

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

Auth and ownership semantics are well covered, but with no output schema the description says nothing about what a successful call returns (card id, principal, registration state), and given idempotentHint=false and the approval-related siblings it is silent on duplicate handling and whether the card becomes active immediately.

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

Parameters3/5

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

Schema coverage is 100% and the nested request description already explains the A2A manifest and the base64 SubjectPublicKeyInfo requirement. The description adds only the consequence of setting signingPublicKey (the initial signing key is registered at the same time), which is modest added value over an already-complete schema.

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

Purpose4/5

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

States a specific verb and resource ("Registers a new agent card") plus the sharp scope constraint that the card lands under the CALLER's own principal, and mentions the conditional RFC 9421 signing key. It does not distinguish itself from the closely named sibling self_register_agent_card, which is the main ambiguity an agent would face.

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?

It gives one real usage prerequisite (a sponsor's Entra bearer token is required) and states the ownership restriction, which is a de facto constraint on when this call is appropriate. It never says when to choose this over self_register_agent_card or the approve_agent_self_registration flow, so the routing decision is left to inference.

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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