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Compare two players' libraries

compare_players

Read-only

Find every game two Steam players both own, with each one's playtime, to see what you and a friend can play together. Compares full libraries rather than a truncated list.

Instructions

Find games two players both own, with each one's playtime — 'what can my friend and I both play', 'do we have anything in common'. Checks each player's FULL library to find every shared game, unlike get_owned_games whose own list stops at 50 by playtime by default — but the returned list here is itself capped at the top 50 shared games by combined playtime (check returned vs shared_count). Requires STEAM_API_KEY and both profiles' game-details to be public. A private profile, or a SteamID64 with no account behind it, returns found:false; an upstream failure returns a tool error worth retrying. Omit steamid to compare against yourself (STEAM_ID).

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": {
      "other_steamid": "<other_steamid>"
    },
    "name": "compare_players"
  }
}

Input Schema

Name	Required	Description	Default
`steamid`	No	17-digit SteamID64. Omit to use the STEAM_ID configured on the server. Convert a vanity/custom URL name with resolve_vanity_url first.
`other_steamid`	Yes	The other player's 17-digit SteamID64 to compare against. Convert a vanity/custom profile name with resolve_vanity_url first.

Output Schema

Name	Required	Description	Default
No arguments

Schema Changelog

Changes observed during successful MCP inspections.

Changed1 schema field changedv0.14.0Sep 27, 2026

changedOutput schema / oneOf

Previous value: -[
-  {
-    "additionalProperties": false,
-    "properties": {
-      "found": {
-        "const": false,
-        "type": "boolean"
-      },
-      "reason": {
-        "type": "string"
-      }
-    },
-    "required": [
-      "found",
-      "reason"
-    ],
-    "type": "object"
-  },
-  {
-    "additionalProperties": false,
-    "properties": {
-      "found": {
-        "const": true,
-        "type": "boolean"
-      },
-      "games": {
-        "items": {
-          "additionalProperties": false,
-          "properties": {
-            "appid": {
-              "type": "number"
-            },
-            "name": {
-              "anyOf": [
-                {
-                  "type": "string"
-                },
-                {
-                  "type": "null"
-                }
-              ]
-            },
-            "playtime_hours_a": {
-              "anyOf": [
-                {
-                  "type": "number"
-                },
-                {
-                  "type": "null"
-                }
-              ]
-            },
-            "playtime_hours_b": {
-              "anyOf": [
-                {
-                  "type": "number"
-                },
-                {
-                  "type": "null"
-                }
-              ]
-            }
-          },
-          "required": [
-            "name",
-            "playtime_hours_a",
-            "playtime_hours_b"
-          ],
-          "type": "object"
-        },
-        "type": "array"
-      },
-      "returned": {
-        "type": "number"
-      },
-      "shared_count": {
-        "type": "number"
-      }
-    },
-    "required": [
-      "found",
-      "shared_count",
-      "returned",
-      "games"
-    ],
-    "type": "object"
-  }
-]New value: +[
+  {
+    "additionalProperties": false,
+    "properties": {
+      "found": {
+        "const": false,
+        "type": "boolean"
+      },
+      "reason": {
+        "type": "string"
+      }
+    },
+    "required": [
+      "found",
+      "reason"
+    ],
+    "type": "object"
+  },
+  {
+    "additionalProperties": false,
+    "properties": {
+      "found": {
+        "const": true,
+        "type": "boolean"
+      },
+      "games": {
+        "items": {
+          "additionalProperties": false,
+          "properties": {
+            "appid": {
+              "type": "number"
+            },
+            "name": {
+              "type": [
+                "string",
+                "null"
+              ]
+            },
+            "playtime_hours_a": {
+              "type": [
+                "number",
+                "null"
+              ]
+            },
+            "playtime_hours_b": {
+              "type": [
+                "number",
+                "null"
+              ]
+            }
+          },
+          "required": [
+            "name",
+            "playtime_hours_a",
+            "playtime_hours_b"
+          ],
+          "type": "object"
+        },
+        "type": "array"
+      },
+      "returned": {
+        "type": "number"
+      },
+      "shared_count": {
+        "type": "number"
+      }
+    },
+    "required": [
+      "found",
+      "shared_count",
+      "returned",
+      "games"
+    ],
+    "type": "object"
+  }
+]

Changed1 schema field changedv0.13.1Aug 17, 2026

changedInput schema / properties / other_steamid / description

Previous value: -"The other player's 17-digit SteamID64 to compare against."New value: +"The other player's 17-digit SteamID64 to compare against. Convert a vanity/custom profile name with resolve_vanity_url first."

Changed3 schema fields changedv0.12.1Jul 30, 2026

addedInput schema / additionalProperties
```
Added value: +false
```

removedOutput schema / anyOf

Removed value: -[
-  {
-    "additionalProperties": false,
-    "properties": {
-      "found": {
-        "const": false,
-        "type": "boolean"
-      },
-      "reason": {
-        "type": "string"
-      }
-    },
-    "required": [
-      "found",
-      "reason"
-    ],
-    "type": "object"
-  },
-  {
-    "additionalProperties": false,
-    "properties": {
-      "found": {
-        "const": true,
-        "type": "boolean"
-      },
-      "games": {
-        "items": {
-          "additionalProperties": false,
-          "properties": {
-            "appid": {
-              "type": "number"
-            },
-            "name": {
-              "anyOf": [
-                {
-                  "type": "string"
-                },
-                {
-                  "type": "null"
-                }
-              ]
-            },
-            "playtime_hours_a": {
-              "anyOf": [
-                {
-                  "type": "number"
-                },
-                {
-                  "type": "null"
-                }
-              ]
-            },
-            "playtime_hours_b": {
-              "anyOf": [
-                {
-                  "type": "number"
-                },
-                {
-                  "type": "null"
-                }
-              ]
-            }
-          },
-          "required": [
-            "name",
-            "playtime_hours_a",
-            "playtime_hours_b"
-          ],
-          "type": "object"
-        },
-        "type": "array"
-      },
-      "returned": {
-        "type": "number"
-      },
-      "shared_count": {
-        "type": "number"
-      }
-    },
-    "required": [
-      "found",
-      "shared_count",
-      "returned",
-      "games"
-    ],
-    "type": "object"
-  }
-]

addedOutput schema / oneOf

Added value: +[
+  {
+    "additionalProperties": false,
+    "properties": {
+      "found": {
+        "const": false,
+        "type": "boolean"
+      },
+      "reason": {
+        "type": "string"
+      }
+    },
+    "required": [
+      "found",
+      "reason"
+    ],
+    "type": "object"
+  },
+  {
+    "additionalProperties": false,
+    "properties": {
+      "found": {
+        "const": true,
+        "type": "boolean"
+      },
+      "games": {
+        "items": {
+          "additionalProperties": false,
+          "properties": {
+            "appid": {
+              "type": "number"
+            },
+            "name": {
+              "anyOf": [
+                {
+                  "type": "string"
+                },
+                {
+                  "type": "null"
+                }
+              ]
+            },
+            "playtime_hours_a": {
+              "anyOf": [
+                {
+                  "type": "number"
+                },
+                {
+                  "type": "null"
+                }
+              ]
+            },
+            "playtime_hours_b": {
+              "anyOf": [
+                {
+                  "type": "number"
+                },
+                {
+                  "type": "null"
+                }
+              ]
+            }
+          },
+          "required": [
+            "name",
+            "playtime_hours_a",
+            "playtime_hours_b"
+          ],
+          "type": "object"
+        },
+        "type": "array"
+      },
+      "returned": {
+        "type": "number"
+      },
+      "shared_count": {
+        "type": "number"
+      }
+    },
+    "required": [
+      "found",
+      "shared_count",
+      "returned",
+      "games"
+    ],
+    "type": "object"
+  }
+]

Addedv0.10.2Jul 22, 2026
Removedv0.8.1Jul 18, 2026
Addedv0.8.0Jul 17, 2026

TDQS

A4.6/5.0

Behavior5/5

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

Annotations only declare readOnlyHint and openWorldHint; the description adds substantial context beyond them: it discloses the 50-item return cap and how to detect truncation via returned vs shared_count, the STEAM_API_KEY and public-profile requirements, the found:false outcome for private or nonexistent accounts, and that upstream failures are retryable.

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?

Purpose and the distinguishing comparison are front-loaded, and every subsequent sentence conveys a distinct constraint (cap, auth, failure modes). It is dense but not padded; a single long paragraph makes the error-mode details slightly harder to scan.

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 an output schema present, the description needn't explain return values, and it still covers the operative constraints: auth requirement, profile visibility, result truncation, and failure semantics. Nothing an agent needs to call it correctly or interpret results is missing.

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%, so both parameters including the omit-to-default behavior and vanity URL conversion are already documented in the schema. The description restates the omit-steamid default but adds no syntax or format detail beyond it, so baseline 3 applies.

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 ('Find games two players both own') and immediately differentiates from the sibling get_owned_games by explaining what that tool does differently. An agent can identify the right tool without opening either schema.

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

Usage Guidelines5/5

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

Includes concrete trigger phrasings ('what can my friend and I both play'), names the alternative tool it supersedes, and explicitly says how to compare against yourself by omitting steamid. When-to-use is unambiguous.

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