The sample
OpenApps tracks the remote MCP servers that store listings link to. A server is "open" when it lists its tools without a sign-in; open servers are the only ones whose full tool definitions anyone outside a signed-in client can read. This census covers our wider MCP dataset: the 425 open servers we track across every store, not only the 105 behind ChatGPT and Claude listings, with 7,777 tools on October 13, 2026.
Behind ChatGPT and Claude listings specifically, we track 727 servers, all linked from Claude listings because ChatGPT publishes no server addresses. 105 of those are open, with 1,541 tools between them. Counting one server that no longer answers openly but keeps an earlier stored list, tools are visible on 106 servers, 1,549 tools in all.
Tools per server
Most servers are small. The median open server in the dataset exposes 7 tools and the 90th percentile 39. Behind Claude listings, 78 of the 105 open servers have 10 tools or fewer, and the largest, api.duvo.ai, has 400.
The largest servers wrap an API one endpoint at a time: api.duvo.ai (400), mcp.datacamp.com (101), api.athenahq.ai (96) and api.tineo.ai (80). Hundreds of similar tools are harder for a model to tell apart than ten.
Annotations
Annotations are hints a tool gives about itself: whether it only reads, whether it can destroy data, whether repeating it is safe, and whether it reaches outside the service. Clients use them to decide when to ask the user first. Adoption is high.
readOnlyHint is set on 91% of tools and is true on 66%: two thirds of all tools say they only read. destructiveHint is set on 85% and true on 9%. These are self-declared; OpenApps doesn't test them.
Output schemas
An output schema tells the client what a tool returns, so it can parse the result without guessing. Only 39% of tools declare one, on 46% of servers. It is the clearest gap in the dataset: most servers describe their inputs carefully and their outputs not at all. 31% of tools carry a _meta object.
Descriptions and parameters
Tool descriptions run a median of 350 characters, with 10% longer than 1,102. Tools take a median of 3 parameters (90th percentile 7); 7% take none, and 67% have at least one required parameter. The most common parameter names are about paging and search:
| Parameter | Tools | Servers |
|---|---|---|
limit | 1,011 | 211 |
query | 420 | 187 |
name | 318 | 103 |
id | 307 | 76 |
category | 143 | 70 |
sort | 90 | 66 |
url | 121 | 63 |
title | 153 | 61 |
offset | 248 | 59 |
cursor | 181 | 57 |
Protocol version and sign-in
94% of open servers support MCP protocol version 2025-06-18; 11 use 2025-03-26, 9 use 2024-11-05, 4 use 2025-11-25 and 1 use 2025-11-05. This measures support for 2025-06-18, not which version servers prefer. Behind Claude listings, 575 of 727 servers (79%) ask for a sign-in before they list anything, 506 of them through OAuth. Those servers' tools are invisible to anyone who hasn't connected, which is why tools are visible for so few listings.
Method and limits
- Tool lists are the public ones: what a server lists without a sign-in. A server can show more to a signed-in user.
- Tool-level shares cover the whole MCP dataset of 425 open servers, not only the 105 behind ChatGPT and Claude listings.
- Annotations and schemas are what servers declare. A tool that says it only reads may still write.
- A new version is recorded only when a tool list changes.