Riot Games

Summoner Top Mastery

summoner_top_mastery

Read-onlyIdempotent

Highest champion mastery entries for one League of Legends account from the Riot Games API, given a puuid and a platform routing value such as na1, euw1, or kr, with count controlling how many champions come back (default 3). Returns championId, championLevel, championPoints, last play time, and chest and token flags for those champions. Answers which champions a League of Legends player has played most and mastered furthest.

Input Schema

Name	Required	Description	Default
`count`	No
`puuid`	Yes
`platform`	Yes

Output Schema

Name	Required	Description	Default
`count`	Yes	Number of items returned.
`items`	Yes	Top N champion mastery entries

Schema Changelog

Changes observed during successful MCP inspections.

Changed2 schema fields changedMay 27, 2026

addedInput schema / examples

Added value: +[
+  {
+    "count": 5,
+    "platform": "na1",
+    "puuid": "player-puuid-123456"
+  }
+]

changedOutput schema / (root)

Previous value: -nullNew value: +{
+  "properties": {
+    "count": {
+      "description": "Number of items returned.",
+      "type": "integer"
+    },
+    "items": {
+      "description": "Top N champion mastery entries",
+      "items": {
+        "properties": {
+          "championId": {
+            "description": "Champion ID",
+            "type": "number"
+          },
+          "championLevel": {
+            "description": "Mastery level",
+            "type": "number"
+          },
+          "championPoints": {
+            "description": "Mastery points",
+            "type": "number"
+          },
+          "lastPlayTime": {
+            "description": "Last play time timestamp",
+            "type": "number"
+          }
+        },
+        "type": "object"
+      },
+      "type": "array"
+    }
+  },
+  "required": [
+    "items",
+    "count"
+  ],
+  "type": "object"
+}

First observedMay 20, 2026

TDQS

A4.6/5.0

Behavior4/5

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

The description discloses the default count of 3, the return fields (championId, championLevel, championPoints, last play time, chest/token flags), and the data source (Riot Games API). These go beyond the annotations' read-only/idempotent hints, providing concrete behavior without contradicting the annotations.

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 three sentences, front-loading the core purpose in the first sentence, then specifying return fields and the higher-level question answered. No filler words, and every sentence adds value.

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?

Given there are only 3 parameters, an output schema, and annotations covering safety, the description provides all necessary context: parameters, defaults, return fields, and use case. It is complete for an AI agent to select and invoke the tool correctly.

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

Parameters5/5

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

The schema provides zero descriptions for any of the three parameters, but the description compensates fully: it defines puuid as 'one League of Legends account', platform as 'platform routing value such as na1, euw1, or kr', and count as 'controlling how many champions come back (default 3)'. This gives complete semantic meaning for invocation.

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 names a specific resource ('highest champion mastery entries for one League of Legends account') with a clear verb ('Returns'), and includes the question it answers ('which champions a League of Legends player has played most and mastered furthest'). This distinguishes it from generic sibling tools like champion_mastery by emphasizing 'highest' and 'top mastery'.

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 invocation parameters (puuid, platform, count) and states the intended use case (answering most-played/mastered champions). However, it does not mention alternatives or when not to use, so it stops short of full usage guidance.

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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