Problem: The MCP server at

http://ipaddress:80/mcp

is returning tool definitions where

outputSchema.additionalProperties

is an object (e.g.,

{ type: "string" }

), but according to JSON Schema specification and the MCP SDK's validation,

additionalProperties

must be a boolean value (

true

or

false

). Relevant Code: The error occurs in the client connection flow: - File:

src/providers/mcp/client.ts

(or

.js

in dist) - Method:

MCPClient.connectToServer()

- Line: Around line 203 (based on stack trace) - Specific operation: After

await client.connect(transport, requestOptions)

succeeds and during

await client.listTools(undefined, requestOptions)

The validation happens within the MCP SDK's

listTools()

method before the response is returned to the client code. Question: Is this a server-side issue that needs to be fixed in the MCP server implementation, or should the client SDK be more lenient and automatically coerce object-type

additionalProperties

to boolean

true

? According to JSON Schema spec,

additionalProperties

as an object is valid (it defines a schema for additional properties), but the MCP SDK appears to only accept boolean values. Configuration:

yaml
mcp:
  enabled: true
  debug: true
  verbose: true
  pingOnConnect: true
  timeout: 120000
  servers:
    - name: web-search
      type: "streamable-http"
      url: "http://ipaddress:80/mcp"

Expected Behavior: Either: 1. The MCP server should return

additionalProperties: true

(or

false

) instead of an object, OR 2. The MCP SDK should accept object-type

additionalProperties

and handle it appropriately Workaround Needed: Is there a way to intercept and sanitize the tool schemas before SDK validation, or does this need to be fixed at the server level?