wa_list_accountsList the WhatsApp accounts available to you. Call this first: every other wa_ tool needs an account_id from here. An account is only usable while its state is "connected".
| Name | Required | Description | Default |
|---|---|---|---|
No arguments | |||
| Name | Required | Description | Default |
|---|---|---|---|
| accounts | Yes | the WhatsApp accounts this API key can use |
Changes observed during successful MCP inspections.
Output schema / properties / accounts / items / properties / backendAdded value: +{
+ "description": "the account's backend: official (WhatsApp Business API) or personal (a linked device)",
+ "type": "string"
+}Output schema / properties / accounts / items / properties / featuresAdded value: +{
+ "description": "the functions this number supports, e.g. messaging, templates, groups, calls; call only tools whose function is listed here",
+ "items": {
+ "type": "string"
+ },
+ "type": [
+ "null",
+ "array"
+ ]
+}Output schema / properties / accounts / items / requiredPrevious value: -[
- "account_id",
- "phone",
- "push_name",
- "state"
-]New value: +[
+ "account_id",
+ "phone",
+ "push_name",
+ "state",
+ "backend",
+ "features"
+]Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already declare readOnlyHint=true, so safety is covered. The description adds genuinely useful operational context beyond that: an account is only usable while its state is 'connected', which tells the agent how to interpret results and why a listed account may be unusable. It does not describe ordering or pagination, but with zero parameters that is a minor gap.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.
Is the description appropriately sized, front-loaded, and free of redundancy?
Three short sentences, zero waste, and the highest-value fact (call this first) is front-loaded right after the purpose statement. Nothing could be removed without losing routing information.
Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.
Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?
For a zero-parameter list tool with a full schema and an output schema, the description covers purpose, sequencing, and the key usability constraint. The only unaddressed nuance is what 'available to you' scopes to (permissions versus pairing), which the agent might want stated explicitly.
Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.
Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?
The tool takes no parameters, so the baseline is 4. There is nothing for the description to clarify beyond the implicit scoping of 'available to you', which it does not expand on.
Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.
Does the description clearly state what the tool does and how it differs from similar tools?
States a specific verb (list) and resource (WhatsApp accounts) with explicit scoping ('available to you'). It is immediately distinguishable from every sibling tool, which operate on messages, groups, or calls rather than account enumeration.
Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.
Does the description explain when to use this tool, when not to, or what alternatives exist?
Gives unambiguous when-to-use guidance: 'Call this first: every other wa_ tool needs an account_id from here.' This is an explicit ordering prerequisite that routes the agent correctly against 30+ siblings.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.
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