codex-in-claude

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List Codex models (free)

codex_models

Read-only

Lists Codex model slugs and their advertised reasoning-effort sets, from cache or fallback, to help set model and reasoning_effort parameters.

Instructions

Deprecated: use amicus_models. List Codex model slugs you can pass as model, with each model's advertised reasoning-effort set for reasoning_effort. Free — no model call.

Advisory discovery only: read from Codex's on-disk cache when present, else a bundled fallback (source says which; the fallback carries no effort data). codex exec validates the real slug and the backend validates the real effort, so an unlisted value may still work and a listed one may be unavailable to your account. Same payload as the codex://models resource. Not fingerprint-stable — do not cache it by the capabilities fingerprint.

Input Schema

TableJSON Schema

Name	Required	Description	Default
No arguments

Output Schema

TableJSON Schema

Name	Required	Description	Default
`ok`	Yes

Schema Changelog

Changes observed during successful MCP inspections.

Changed1 schema field changedv0.13.0Jul 15, 2026

changedOutput schema / anyOf

Previous value: -[
-  {
-    "additionalProperties": false,
-    "properties": {
-      "advisory": {
-        "type": "string"
-      },
-      "cache_client_version": {
-        "anyOf": [
-          {
-            "type": "string"
-          },
-          {
-            "type": "null"
-          }
-        ]
-      },
-      "fetched_at": {
-        "anyOf": [
-          {
-            "type": "string"
-          },
-          {
-            "type": "null"
-          }
-        ]
-      },
-      "fingerprint": {
-        "type": "string"
-      },
-      "models": {
-        "items": {
-          "additionalProperties": false,
-          "properties": {
-            "display_name": {
-              "anyOf": [
-                {
-                  "type": "string"
-                },
-                {
-                  "type": "null"
-                }
-              ]
-            },
-            "slug": {
-              "type": "string"
-            }
-          },
-          "required": [
-            "slug"
-          ],
-          "type": "object"
-        },
-        "type": "array"
-      },
-      "ok": {
-        "const": true,
-        "type": "boolean"
-      },
-      "server_version": {
-        "anyOf": [
-          {
-            "type": "string"
-          },
-          {
-            "type": "null"
-          }
-        ]
-      },
-      "source": {
-        "enum": [
-          "cache",
-          "static",
-          "none"
-        ],
-        "type": "string"
-      },
-      "unavailable_reason": {
-        "anyOf": [
-          {
-            "type": "string"
-          },
-          {
-            "type": "null"
-          }
-        ]
-      }
-    },
-    "required": [
-      "source",
-      "advisory"
-    ],
-    "type": "object"
-  },
-  {
-    "properties": {
-      "error": {
-        "description": "Populated error envelope; full schema at resource codex://error-envelope",
-        "type": "object"
-      },
-      "meta": {
-        "type": "object"
-      },
-      "ok": {
-        "const": false
-      }
-    },
-    "required": [
-      "ok",
-      "error",
-      "meta"
-    ],
-    "type": "object"
-  }
-]New value: +[
+  {
+    "additionalProperties": false,
+    "properties": {
+      "advisory": {
+        "type": "string"
+      },
+      "cache_client_version": {
+        "anyOf": [
+          {
+            "type": "string"
+          },
+          {
+            "type": "null"
+          }
+        ]
+      },
+      "fetched_at": {
+        "anyOf": [
+          {
+            "type": "string"
+          },
+          {
+            "type": "null"
+          }
+        ]
+      },
+      "fingerprint": {
+        "type": "string"
+      },
+      "models": {
+        "items": {
+          "additionalProperties": false,
+          "properties": {
+            "default_reasoning_effort": {
+              "anyOf": [
+                {
+                  "type": "string"
+                },
+                {
+                  "type": "null"
+                }
+              ],
+              "description": "This model's default reasoning effort as advertised by Codex's on-disk cache; advisory only. null = the cache advertised nothing usable (the static fallback never carries effort data)."
+            },
+            "display_name": {
+              "anyOf": [
+                {
+                  "type": "string"
+                },
+                {
+                  "type": "null"
+                }
+              ]
+            },
+            "slug": {
+              "type": "string"
+            },
+            "supported_reasoning_efforts": {
+              "anyOf": [
+                {
+                  "items": {
+                    "type": "string"
+                  },
+                  "type": "array"
+                },
+                {
+                  "type": "null"
+                }
+              ],
+              "description": "Effort tokens this model advertises in Codex's on-disk cache; advisory only — the backend's accepted set varies by account and an unlisted effort may still work. null = the cache advertised nothing usable; [] = an explicitly empty advertised set."
+            }
+          },
+          "required": [
+            "slug"
+          ],
+          "type": "object"
+        },
+        "type": "array"
+      },
+      "ok": {
+        "const": true,
+        "type": "boolean"
+      },
+      "server_version": {
+        "anyOf": [
+          {
+            "type": "string"
+          },
+          {
+            "type": "null"
+          }
+        ]
+      },
+      "source": {
+        "enum": [
+          "cache",
+          "static",
+          "none"
+        ],
+        "type": "string"
+      },
+      "unavailable_reason": {
+        "anyOf": [
+          {
+            "type": "string"
+          },
+          {
+            "type": "null"
+          }
+        ]
+      }
+    },
+    "required": [
+      "source",
+      "advisory"
+    ],
+    "type": "object"
+  },
+  {
+    "properties": {
+      "error": {
+        "description": "Populated error envelope; full schema at resource codex://error-envelope",
+        "type": "object"
+      },
+      "meta": {
+        "type": "object"
+      },
+      "ok": {
+        "const": false
+      }
+    },
+    "required": [
+      "ok",
+      "error",
+      "meta"
+    ],
+    "type": "object"
+  }
+]

Changed1 schema field changedv0.11.0Jul 14, 2026

changedOutput schema / anyOf

Previous value: -[
-  {
-    "additionalProperties": false,
-    "properties": {
-      "advisory": {
-        "type": "string"
-      },
-      "cache_client_version": {
-        "anyOf": [
-          {
-            "type": "string"
-          },
-          {
-            "type": "null"
-          }
-        ]
-      },
-      "fetched_at": {
-        "anyOf": [
-          {
-            "type": "string"
-          },
-          {
-            "type": "null"
-          }
-        ]
-      },
-      "fingerprint": {
-        "type": "string"
-      },
-      "models": {
-        "items": {
-          "additionalProperties": false,
-          "properties": {
-            "display_name": {
-              "anyOf": [
-                {
-                  "type": "string"
-                },
-                {
-                  "type": "null"
-                }
-              ]
-            },
-            "slug": {
-              "type": "string"
-            }
-          },
-          "required": [
-            "slug"
-          ],
-          "type": "object"
-        },
-        "type": "array"
-      },
-      "ok": {
-        "const": true,
-        "type": "boolean"
-      },
-      "source": {
-        "enum": [
-          "cache",
-          "static",
-          "none"
-        ],
-        "type": "string"
-      },
-      "unavailable_reason": {
-        "anyOf": [
-          {
-            "type": "string"
-          },
-          {
-            "type": "null"
-          }
-        ]
-      }
-    },
-    "required": [
-      "source",
-      "advisory"
-    ],
-    "type": "object"
-  },
-  {
-    "properties": {
-      "error": {
-        "description": "Populated error envelope; full schema at resource codex://error-envelope",
-        "type": "object"
-      },
-      "meta": {
-        "type": "object"
-      },
-      "ok": {
-        "const": false
-      }
-    },
-    "required": [
-      "ok",
-      "error",
-      "meta"
-    ],
-    "type": "object"
-  }
-]New value: +[
+  {
+    "additionalProperties": false,
+    "properties": {
+      "advisory": {
+        "type": "string"
+      },
+      "cache_client_version": {
+        "anyOf": [
+          {
+            "type": "string"
+          },
+          {
+            "type": "null"
+          }
+        ]
+      },
+      "fetched_at": {
+        "anyOf": [
+          {
+            "type": "string"
+          },
+          {
+            "type": "null"
+          }
+        ]
+      },
+      "fingerprint": {
+        "type": "string"
+      },
+      "models": {
+        "items": {
+          "additionalProperties": false,
+          "properties": {
+            "display_name": {
+              "anyOf": [
+                {
+                  "type": "string"
+                },
+                {
+                  "type": "null"
+                }
+              ]
+            },
+            "slug": {
+              "type": "string"
+            }
+          },
+          "required": [
+            "slug"
+          ],
+          "type": "object"
+        },
+        "type": "array"
+      },
+      "ok": {
+        "const": true,
+        "type": "boolean"
+      },
+      "server_version": {
+        "anyOf": [
+          {
+            "type": "string"
+          },
+          {
+            "type": "null"
+          }
+        ]
+      },
+      "source": {
+        "enum": [
+          "cache",
+          "static",
+          "none"
+        ],
+        "type": "string"
+      },
+      "unavailable_reason": {
+        "anyOf": [
+          {
+            "type": "string"
+          },
+          {
+            "type": "null"
+          }
+        ]
+      }
+    },
+    "required": [
+      "source",
+      "advisory"
+    ],
+    "type": "object"
+  },
+  {
+    "properties": {
+      "error": {
+        "description": "Populated error envelope; full schema at resource codex://error-envelope",
+        "type": "object"
+      },
+      "meta": {
+        "type": "object"
+      },
+      "ok": {
+        "const": false
+      }
+    },
+    "required": [
+      "ok",
+      "error",
+      "meta"
+    ],
+    "type": "object"
+  }
+]

Changed1 schema field changedv0.8.0Jul 6, 2026
- addedOutput schema / $schema
```
Added value: +"https://json-schema.org/draft/2020-12/schema"
```
First observedv0.5.0Jun 28, 2026

TDQS

A4.6/5.0

Behavior5/5

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

Goes well beyond the readOnlyHint/openWorldHint annotations: discloses the cache-vs-bundled-fallback source, that the fallback lacks effort data, that validation happens in `codex exec`/backend, that listed values may be unavailable, and that it is not fingerprint-stable and should not be cached. This is exactly the extra behavioral context annotations cannot carry.

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?

Front-loaded with the deprecation and core purpose, then layers caveats efficiently. It is dense rather than bloated, though the caveat block is long enough to keep it just under maximum.

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?

An output schema exists so return values need not be explained, yet the description still clarifies the `source` field and the fallback's limitations. For a zero-param discovery tool, an agent has everything needed to call and interpret it.

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?

Zero parameters means the baseline is 4. The description nonetheless adds meaning by explaining that the returned slugs feed the `model` parameter and the effort sets feed `reasoning_effort`, which is useful consumer-facing context.

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?

States a specific verb and resource ('List Codex model slugs') and immediately scopes what the values are for ('pass as `model`', 'reasoning_effort'). The deprecation notice and pointer to amicus_models cleanly separate it from siblings.

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?

Explicitly names the replacement (amicus_models) and frames the tool as 'advisory discovery only' with no model call. It does not spell out a when-not-to-use condition beyond the deprecation, so it stops short of the top score.

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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