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SMS and WhatsApp Messaging

by dev.hatchloop
OverviewDiscussionsAdmin

send_message

Destructive

Send a message on behalf of an agent's user or an SMB across WhatsApp (free during launch), SMS, email, or voice, sent immediately, no scheduling. Every send passes a non-bypassable gate: TCPA, GDPR, CASL where modeled, else the service's own opt-in default (the Gulf included). Marketing on SMS, voice, WhatsApp and non-US email without recorded opt-in is rejected (compliance_violation receipt). US marketing email follows CAN-SPAM opt-out rules. [from $0.02/call, variable, not charged while no payment rail is on] [async→get_outcome] [Not available on this deployment: SMS, Voice.]

Input Schema

TableJSON Schema
NameRequiredDescriptionDefault
contentYes
recipientYes
business_idNoStable id for the recipient business; used for global demand shaping.
message_typeYes'marketing' needs recorded opt-in, except US email (CAN-SPAM opt-out rules).…
on_behalf_ofNoWho this message is FOR (your end-user's name/label). On WhatsApp this opens a…
idempotency_keyNoRetry key: a 24h replay returns the original receipt, not re-run or charged.
preferred_channelNoauto

Schema Changelog

Changes observed during successful MCP inspections.

  1. Changed1 schema field changed
    • changedInput schema / properties / message_type / description
      Previous value: -"Intent tag for the message. Five permitted types. 'marketing' is allowed only…"New value: +"'marketing' needs recorded opt-in, except US email (CAN-SPAM opt-out rules).…"
  2. Changed3 schema fields changed
    • changedInput schema / properties / business_id / description
      Previous value: -"Optional stable id for the recipient business. Enables global demand shaping…"New value: +"Stable id for the recipient business; used for global demand shaping."
    • changedInput schema / properties / idempotency_key / description
      Previous value: -"Optional client-supplied key for safe retries. Replaying the same key within 24h returns the original receipt - the operation is NOT re-executed and NOT re-charged."New value: +"Retry key: a 24h replay returns the original receipt, not re-run or charged."
    • removedInput schema / properties / send_at_iso
      Removed value: -{
-  "description": "NOT SUPPORTED YET. We do not schedule messages. Supplying a time more than 2…",
-  "format": "date-time",
-  "type": "string"
-}
  3. Changed4 schema fields changed
    • changedInput schema / properties / business_id / description
      Previous value: -"Optional stable id for the recipient business. Enables global demand shaping (we rate-limit total inbound across ALL agents so businesses stay responsive instead of blocking us)."New value: +"Optional stable id for the recipient business. Enables global demand shaping…"
    • changedInput schema / properties / message_type / description
      Previous value: -"Intent tag for the message. Five permitted types. 'marketing' is allowed only when paired with a valid consent_record_id; the compliance gate verifies the consent at send time and rejects (compliance_violation receipt) if it's missing, expired, or revoked."New value: +"Intent tag for the message. Five permitted types. 'marketing' is allowed only…"
    • changedInput schema / properties / on_behalf_of / description
      Previous value: -"Who this message is FOR (your end-user's name/label). On WhatsApp this opens a tracked conversation and travels in-message as '#4821 for Sara (via HatchLoop)', so the business knows who it is talking to and their reply is matched back to this exact request instead of guessed. Strongly recommended for two-way channels."New value: +"Who this message is FOR (your end-user's name/label). On WhatsApp this opens a…"
    • changedInput schema / properties / send_at_iso / description
      Previous value: -"NOT SUPPORTED YET. We do not schedule messages. Supplying a time more than 2 minutes in the future is REFUSED (reason_code scheduling_not_supported) rather than sent immediately, which is what used to happen. Call send_message at the moment you want delivery, or omit this field."New value: +"NOT SUPPORTED YET. We do not schedule messages. Supplying a time more than 2…"
  4. First observed

TDQS

A4.2/5.0
Behavior5/5

Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

Goes well past the annotations: a non-bypassable compliance gate (TCPA/GDPR/CASL or the service default), a named rejection artifact (compliance_violation receipt), cost behavior ($0.02/call, not charged while no payment rail is on), async execution requiring get_outcome, and deployment-limited channels. These are exactly the side effects and failure modes an agent must know before invoking a destructive, open-world send.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Conciseness4/5

Is the description appropriately sized, front-loaded, and free of redundancy?

Front-loaded with the core action and scope in the first clause, so an agent gets the gist immediately. The trailing bracket block (pricing, async routing, deployment limits) is dense and slightly cluttered, but each item carries operational value rather than filler.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Completeness4/5

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

For a 7-parameter, nested-schema, highly regulated tool with no output schema, the description covers the decision-critical context: compliance gating, rejection behavior, cost, async outcome path, and channel availability. It does not describe the success receipt shape or authentication/permission requirements, which would fully round it out.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Parameters4/5

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

With 57% schema coverage, the description meaningfully compensates: it enumerates the usable channels in prose (WhatsApp/SMS/email/voice with availability caveats), ties message_type to consent rules, and explains the regulatory dimension behind country_code routing. It says nothing about business_id, on_behalf_of, idempotency_key, or template usage, so a few parameters remain schema-only.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Purpose4/5

Does the description clearly state what the tool does and how it differs from similar tools?

States a specific verb and resource plus scope: send a single message on behalf of a user/SMB across WhatsApp, SMS, email, or voice, immediately with no scheduling. The channel enumeration and compliance framing make the operation unambiguous. It does not name the sibling that overlaps most (send_transactional_confirmation), so the agent can't fully disambiguate from siblings on this description alone.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Usage Guidelines4/5

Does the description explain when to use this tool, when not to, or what alternatives exist?

Gives real routing conditions: messages are immediate (no scheduling), marketing is rejected without recorded opt-in on most channels, US marketing email follows CAN-SPAM, and async results are routed to get_outcome. It also flags deployment limits (SMS and Voice unavailable here), which prevents an agent from selecting an unusable channel. No explicit 'use X instead of Y' comparison against send_transactional_confirmation or check_compliance is given.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.

All SMS and WhatsApp Messaging toolsInspect
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