issue: Reference MCP Server (elasticsearch) not compatible with mcpo

[dmytryk-here]

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I am using the latest version of mcpo.

mcpo Version
v0.0.17

hi all,

I'm trying to run elasticsearch mcp (https://github.com/elastic/mcp-server-elasticsearch) in mcpo, using streaming http. for some reason mcpo openapi.json, doesn't return proper tools description. connecting to the same elasticsearch mcp, using mcp inspector works as expected. here are the outputs:
curl -L http://localhost:3010/elasticsearch/openapi.json {"openapi":"3.1.0","info":{"title":"elasticsearch","description":"elasticsearch MCP Server\n\n- [back to tool list](/docs)","version":"1.0"},"servers":[{"url":"/elasticsearch"}],"paths":{}}
while mcp inspector returns a proper tool list:
search Perform an Elasticsearch search with the provided query DSL. esql Perform an Elasticsearch ES|QL query. list_indices List all available Elasticsearch indices get_shards Get shard information for all or specific indices. get_mappings Get field mappings for a specific Elasticsearch index

here is the log of the elasticsearch mcp container, when using mcp inspector:

elasticsearch-1 | 2025-08-21T08:56:36.568277Z INFO rmcp::transport::streamable_http_server::tower: Response(JsonRpcResponse { jsonrpc: JsonRpcVersion2_0, id: Number(6), result: ListToolsResult(ListToolsResult { next_cursor: None, tools: [Tool { name: "search", description: Some("Perform an Elasticsearch search with the provided query DSL."), input_schema: {"$schema": String("http://json-schema.org/draft-07/schema#"), "properties": Object {"fields": Object {"description": String("Name of the fields that need to be returned (optional)"), "items": Object {"type": String("string")}, "nullable": Bool(true), "type": String("array")}, "index": Object {"description": String("Name of the Elasticsearch index to search"), "type": String("string")}, "query_body": Object {"additionalProperties": Bool(true), "description": String("Complete Elasticsearch query DSL object that can include query, size, from, sort, etc."), "type": String("object")}}, "required": Array [String("index"), String("query_body")], "title": String("SearchParams"), "type": String("object")}, annotations: Some(ToolAnnotations { title: Some("Elasticsearch search DSL query"), read_only_hint: Some(true), destructive_hint: None, idempotent_hint: None, open_world_hint: None }) }, Tool { name: "esql", description: Some("Perform an Elasticsearch ES|QL query."), input_schema: {"$schema": String("http://json-schema.org/draft-07/schema#"), "properties": Object {"query": Object {"description": String("Complete Elasticsearch ES|QL query"), "type": String("string")}}, "required": Array [String("query")], "title": String("EsqlQueryParams"), "type": String("object")}, annotations: Some(ToolAnnotations { title: Some("Elasticsearch ES|QL query"), read_only_hint: Some(true), destructive_hint: None, idempotent_hint: None, open_world_hint: None }) }, Tool { name: "list_indices", description: Some("List all available Elasticsearch indices"), input_schema: {"$schema": String("http://json-schema.org/draft-07/schema#"), "properties": Object {"index_pattern": Object {"description": String("Index pattern of Elasticsearch indices to list"), "type": String("string")}}, "required": Array [String("index_pattern")], "title": String("ListIndicesParams"), "type": String("object")}, annotations: Some(ToolAnnotations { title: Some("List ES indices"), read_only_hint: Some(true), destructive_hint: None, idempotent_hint: None, open_world_hint: None }) }, Tool { name: "get_shards", description: Some("Get shard information for all or specific indices."), input_schema: {"$schema": String("http://json-schema.org/draft-07/schema#"), "properties": Object {"index": Object {"description": String("Optional index name to get shard information for"), "nullable": Bool(true), "type": String("string")}}, "title": String("GetShardsParams"), "type": String("object")}, annotations: Some(ToolAnnotations { title: Some("Get ES shard information"), read_only_hint: Some(true), destructive_hint: None, idempotent_hint: None, open_world_hint: None }) }, Tool { name: "get_mappings", description: Some("Get field mappings for a specific Elasticsearch index"), input_schema: {"$schema": String("http://json-schema.org/draft-07/schema#"), "properties": Object {"index": Object {"description": String("Name of the Elasticsearch index to get mappings for"), "type": String("string")}}, "required": Array [String("index")], "title": String("GetMappingsParams"), "type": String("object")}, annotations: Some(ToolAnnotations { title: Some("Get ES index mappings"), read_only_hint: Some(true), destructive_hint: None, idempotent_hint: None, open_world_hint: None }) }] }) })

What can be the reason for this?

[cybersholt]

Ran into a similar issue testing Codex.

Codex (OpenAI CLI) needs an RMCP (streamable HTTP) MCP endpoint, not OpenAPI. It sends the MCP initialize JSON-RPC to the base URL; MCPO returns 404, so handshake fails.
Please add an RMCP endpoint (or document its path) that implements initialize, tools/list, and tools/call (JSON-RPC 2.0, optional bearer auth).
With that, Codex will connect; right now it only works via STDIO.