docs(mcp): explain conflicting destination streams in create_connection_on_cloud and point to table_prefix #1404

Requested by AJ Steers (Aaron ("AJ") Steers (@aaronsteers)), from a hosted Cloud MCP failure review (Datadog LLM Obs tool spans, Oct 4–16 2026).

Problem

This error is expected Cloud validation, not a bug. Cloud rejects a new connection when any of its streams would write to the same destination table (namespace + name) that another connection on that destination already writes to. The response is 400 error:connection-conflicting-destination-stream:

One or more streams in this connection write to a destination location that another connection already uses. Choose a different namespace or stream prefix for the conflicting streams.

The response's data.streams lists each conflicting stream and the connection IDs it conflicts with.

create_connection_on_cloud already passes the detail text through (since #1368). But the agent still doesn't have what it needs to fix the call:

• data.streams is dropped, so the agent doesn't know which streams clash or which existing connection owns those tables;
• the text says "namespace or stream prefix", but the tool only offers table_prefix (no namespace option), and the error doesn't name that parameter;
• the tool docstring and the table_prefix description ("Optional table prefix to use when syncing to the destination.") don't mention this rule.

Evidence

• Oct 14, one customer (rc.30): the agent was creating several connections from same-type sources into one destination. It hit this error twice, never retried with table_prefix, then tried schema-qualified stream names (also rejected), and in the end selected only the tables whose names didn't clash.
• 4 occurrences in Oct 4–16, all from create_connection_on_cloud.

Proposed fix (guidance only)

1. create_connection_on_cloud docstring: say that two connections into the same destination can't write to the same table name, and that table_prefix (for example <source>_) is the way to keep them apart.
2. table_prefix field description: mention the same rule.
3. On connection-conflicting-destination-stream, add guidance that names table_prefix and lists the conflicting stream names and connection IDs from data.streams (if this is too verbose, cap the list).

Written by Devin