MCP server seems to only accept required fields when generating input to run actors

[vincent-homeric]

Edit: If it's actually a bug (and not a feature ;-) ) it was created by 25ca155
Edit 2: Happy to confirm that forcing the loading of the previous version 0.2.9 in my Claude config file is a functional workaround.

I use bebity/linkedin-jobs-scraper daily and here is a typical input:
{
"location": "United States",
"proxy": {
"useApifyProxy": true,
"apifyProxyGroups": [
"RESIDENTIAL"
]
},
"publishedAt": "r86400",
"rows": 50,
"title": "Agile Coach"
}

Only location, rows and title are mandatory. Since this morning, whatever instruction I send to the MCP, it will never include optional fields like publishedAt or proxy. Not being able to use the publishedAt field because it's not required or not an integer makes this actor useless through MCP. Claude's diagnosis:

The issue is that the MCP tool interface doesn't allow me to send a request with invalid fields like "proxy" and "publishedAt" that aren't part of the tool's schema. The tool only accepts the specific parameters it's designed for: "title", "location", and "rows".
Let me check if there's a way to use a more generic actor calling method that would allow me to send the request you provided.

[...]

I see the issue now. Looking at the actor's input schema, it actually DOES accept "proxy" and "publishedAt" as valid fields! The MCP tool interface I used earlier was simplified and only exposed the required fields.
Unfortunately, the current MCP server setup doesn't seem to have a generic "call-actor" tool that would let me send arbitrary input. The individual actor tools are pre-configured with only the required parameters.

[jirispilka]

Hi, thank you for using the MCP server and for the detailed information.

@MQ37 can you please look into this?

[MQ37]

Hey @vincent-homeric,

Including only required and integer fields (so the MCP client can set Actor parameters like limit, maxResults, or similar to control the number of results, which are usually integers) is a feature designed to prevent LLM confusion. Since this caused issues for some Actors with complicated input, we are now filtering the tool input schema. You can pass any additional Actor run input parameters you want.

You should be able to tell Claude to call the bebity/linkedin-jobs-scraper with this input, and it should pass it correctly to the Actor:

"location": "United States",
"proxy": {
  "useApifyProxy": true,
  "apifyProxyGroups": [
    "RESIDENTIAL"
  ]
},
"publishedAt": "r86400",
"rows": 50,
"title": "Agile Coach"
}

Which version of Claude desktop and on what platform are you using? What version of @apify/actors-mcp-server are you running? I am using Claude desktop on Linux with the latest @apify/actors-mcp-server version, and this prompt works for me.

[MQ37]

@vincent-homeric taking my statement back, from my previous testing, I could pass additional parameters to the Actor, but it was in VSCode. Tested with the latest version of Claude desktop, and passing of additional parameters does not work.

@jirispilka this is a breaking change, and we should not filter the input schema by any means, since then some clients will not be able to use all the parameters

[vincent-homeric]

@MQ37 - I get from your last message that you don't need additional input from me. Let me know if I can help :)

[MQ37]

Hey @vincent-homeric, thank you for pointing this out and sorry for the late response. We reverted the input schema filtering and released a new version 0.2.13 of Apify Actors MCP server.

Closing this issue, feel free to reopen if needed.