Add send_to_conversation MCP tool

[latentoperator]

Summary

• Adds a new send_to_conversation MCP tool that sends messages using a conversation ID instead of requiring a phone number
• Enables AI assistants to reply to conversations directly after list_conversations, without needing to resolve the recipient's phone number via list_contacts
• Follows the same pattern as the existing web API send endpoint (/api/conversations/:id/send)

Motivation

When an AI assistant sees an incoming message via list_conversations → get_conversation, the natural next step is to reply. Currently, the only way to send is via send_message which requires a phone number. This forces a detour through list_contacts to look up the number by name — which fails if the contact isn't synced or the name doesn't match exactly.

send_to_conversation closes this gap by accepting the conversation ID that the assistant already has.

Implementation

The handler reuses the same web.BuildSendPayload helper and GetConversation → participant/SIM resolution pattern used by the web API's send endpoint. Includes tests for validation and not-connected cases.

Test plan

• send_to_conversation with valid conversation ID sends message
• Missing conversation_id returns validation error
• Missing message returns validation error
• Not connected to Google Messages returns appropriate error
• Tool registers without panic in TestRegisterTools

🤖 Generated with Claude Code

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