Nexus Catalyst

Get persona definition

get_persona_definition

Read-onlyIdempotent

Returns the full definition, communication style and behavioural guidelines for one named persona from the user's NC persona set.

persona_name takes the value returned as persona_hint by recall_context. A name outside the user's persona set returns a PERSONA_NOT_FOUND error rather than a substitute or an invented definition.

Input Schema

TableJSON Schema

Name	Required	Description	Default
`persona_name`	Yes	Name of the persona to retrieve

Output Schema

TableJSON Schema

Name	Required	Description
`data`	No
`error`	No	On an unknown persona: `{ type, message, persona_name, timestamp }`.
`message`	No
`success`	Yes

Schema Changelog

Changes observed during successful MCP inspections.

Changed1 schema field changedSep 25, 2026

changedOutput schema / (root)

Previous value: -nullNew value: +{
+  "additionalProperties": true,
+  "properties": {
+    "data": {
+      "additionalProperties": true,
+      "properties": {
+        "embodiment_instructions": {
+          "additionalProperties": true,
+          "description": "How to adopt the persona: activation cues, communication pattern, expertise triggers.",
+          "type": "object"
+        },
+        "persona": {
+          "additionalProperties": true,
+          "properties": {
+            "communication_style": {
+              "type": "string"
+            },
+            "expertise": {
+              "items": {
+                "type": "string"
+              },
+              "type": "array"
+            },
+            "name": {
+              "type": "string"
+            },
+            "personality_traits": {
+              "type": "string"
+            },
+            "professional_background": {
+              "type": "string"
+            },
+            "profile": {
+              "type": "string"
+            },
+            "role": {
+              "type": [
+                "object",
+                "string"
+              ]
+            },
+            "roleId": {
+              "type": "string"
+            }
+          },
+          "type": "object"
+        }
+      },
+      "type": "object"
+    },
+    "error": {
+      "description": "On an unknown persona: `{ type, message, persona_name, timestamp }`.",
+      "type": [
+        "object",
+        "boolean",
+        "string"
+      ]
+    },
+    "message": {
+      "type": "string"
+    },
+    "success": {
+      "type": "boolean"
+    }
+  },
+  "required": [
+    "success"
+  ],
+  "type": "object"
+}

First observedSep 16, 2026

TDQS

A4.7/5.0

Behavior5/5

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

Annotations already declare read-only, idempotent, and non-destructive behavior. The description adds meaningful behavior beyond this by disclosing that an out-of-set persona name returns a PERSONA_NOT_FOUND error rather than a substitute or invented definition, which directly addresses failure mode and hallucination risk.

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?

The description is two short paragraphs with no filler. The primary purpose is front-loaded, and the second paragraph efficiently conveys the key parameter source and error behavior.

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

Completeness5/5

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

With only one parameter, annotations covering safety, an output schema, and a description that explains both success content and error behavior, the tool is fully specified for correct invocation. No critical information is missing.

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?

The schema only describes persona_name as 'Name of the persona to retrieve', which is minimal. The description adds crucial semantics by specifying that the correct value comes from recall_context's persona_hint, giving the agent actionable guidance beyond the schema.

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: it returns the full definition, communication style, and behavioral guidelines for one named persona. It clearly distinguishes this from the sibling memory and integration tools by scoping to the user's NC persona set, so an agent can immediately tell what this tool is for.

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

Usage Guidelines4/5

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

The description gives explicit context for obtaining the correct persona_name by referencing the value returned as persona_hint by recall_context. It does not explicitly name alternatives or say when not to use this tool, but the provenance guidance makes the correct usage clear.

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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