App Store Opportunity Tracker

Read a top chart with movers

app_tracker_charts

Read-onlyIdempotent

Use this when the user asks what is on or climbing the App Store top free or top paid chart, such as "top free apps in the US" or "what is climbing the top paid chart?". Pass country, chart (free or paid) and limit. Returns ranked entries with price, rating, rating count and change since an earlier snapshot, plus movers (gainers, losers, new entries, dropped) and apps released in the last 7 days. movers.since is the time of the snapshot compared against; null means there is none yet. Google Play, grossing and genre charts answer source_off: no allowed source publishes them.

Example tool call

This call uses example arguments supplied in the tool’s input schema.

{
  "id": 1,
  "jsonrpc": "2.0",
  "method": "tools/call",
  "params": {
    "arguments": {
      "chart": "free",
      "limit": 5,
      "store": "apple",
      "country": "us"
    },
    "name": "app_tracker_charts"
  }
}

Input Schema

Name	Required	Description
`chart`	No	Which top chart: free (default) or paid. grossing answers source_off: no allowed source publishes it.
`genre`	No	Omit for the overall chart. A genre answers source_off: no allowed source publishes genre charts.
`limit`	No	How many rows to return, 1 to 100. Default 25. The whole chart is always scanned.
`store`	No	apple (App Store, default). play answers source_off: Google Play charts load only through a path its robots.txt disallows.
`country`	No	Two-letter store country, such as us, gb or jp. Default us.

Output Schema

Name	Required	Description
`day`	No
`note`	Yes
`as_of`	Yes	ISO 8601 time the data was published by its source or fetched from it. A cached answer keeps the time of its fetch.
`chart`	Yes
`genre`	No
`stale`	No	Present only when Apple's feed failed and the newest stored copy of the chart, up to 3 days old, was served instead. fetchedAt is that copy's time.
`store`	Yes
`movers`	Yes
`source`	Yes	Who the data comes from, to cite and to check it against.
`country`	Yes
`entries`	Yes
`fetchedAt`	No
`newReleases`	No
`untrusted_source`	Yes

Schema Changelog

Changes observed during successful MCP inspections.

Changed1 schema field changedOct 25, 2026
- addedOutput schema / properties / day
```
Added value: +{
+  "type": [
+    "string",
+    "null"
+  ]
+}
```

Changed1 schema field changedOct 23, 2026

addedOutput schema / properties / stale

Added value: +{
+  "description": "Present only when Apple's feed failed and the newest stored copy of the chart, up to 3 days old, was served instead. fetchedAt is that copy's time.",
+  "properties": {
+    "reason": {
+      "type": "string"
+    },
+    "takenAt": {
+      "type": "string"
+    }
+  },
+  "type": "object"
+}

Changed4 schema fields changedOct 23, 2026

changedInput schema / examples

Previous value: -[
-  {
-    "chart": "free",
-    "country": "us",
-    "genre": "6007",
-    "limit": 5,
-    "store": "apple"
-  }
-]New value: +[
+  {
+    "chart": "free",
+    "country": "us",
+    "limit": 5,
+    "store": "apple"
+  }
+]

changedInput schema / properties / chart / description

Previous value: -"Which top chart. Default free."New value: +"Which top chart: free (default) or paid. grossing answers source_off: no allowed source publishes it."

changedInput schema / properties / genre / description

Previous value: -"Apple genre id such as 6007 (Productivity) or 6013 (Health & Fitness), a Google Play category such as PRODUCTIVITY, or a genre name. Omit for all apps."New value: +"Omit for the overall chart. A genre answers source_off: no allowed source publishes genre charts."

changedInput schema / properties / store / description

Previous value: -"apple (App Store, default) or play (Google Play)."New value: +"apple (App Store, default). play answers source_off: Google Play charts load only through a path its robots.txt disallows."

First observedOct 21, 2026

TDQS

A4.4/5.0

Behavior4/5

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

Annotations already establish read-only, idempotent, open-world, non-destructive behavior, and the description adds valuable context about movers.since semantics (null means no prior snapshot) and the 7-day new-release window. It doesn't discuss pagination or rate limits, and some return-field detail overlaps the output schema, so it lands just below the top.

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 trigger and examples, then output shape, then limitations — a good order. The source_off caveat is repeated in three schema field descriptions, and the trailing sentence partially duplicates them, which costs a bit of tightness.

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 a 5-parameter, all-optional tool with rich annotations and an output schema, the description covers the trigger, key inputs, returned fields, mover semantics, and the exact unsupported combinations. An agent can invoke it correctly without opening the schema, which is the bar for completeness here.

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%, with enums and descriptions for chart, genre, limit, store and country already documenting defaults and constraints. The description's 'Pass country, chart (free or paid) and limit' restates rather than extends that, so the baseline 3 is appropriate.

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 — read the App Store top free/paid chart — and immediately characterizes the output (ranked entries plus movers). It is clearly distinguishable from siblings like app_tracker_lookup or app_tracker_keyword_rank, which deal with individual apps and keyword positions rather than chart rankings.

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?

Opens with an explicit trigger ('Use this when the user asks what is on or climbing the App Store top free or top paid chart') and gives concrete example queries. It also states when-not: Google Play, grossing and genre charts return source_off, so the agent knows not to attempt those paths.

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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