MailFixture

list_sms

List SMS received on a phone number (id, from_number, text, received_at per message — the text rides in the summary). Set wait to long-poll for new messages; use since as a cursor.

Tool call template

Replace each placeholder with a value matching the input schema. Only required parameters are included; add optional parameters as needed.

{
  "id": 1,
  "jsonrpc": "2.0",
  "method": "tools/call",
  "params": {
    "arguments": {
      "phone_number_id": "<phone_number_id>"
    },
    "name": "list_sms"
  }
}

Input Schema

Name	Required	Description
`wait`	No	Long-poll up to this many seconds (max 60) for a matching message instead of returning an empty list immediately.
`match`	No	Filter: `from:term`, `to:term`, or `body:term`; a bare term matches the body.
`since`	No	Only messages received after this RFC 3339 timestamp. Use the received_at of the last message you saw as a cursor.
`phone_number_id`	Yes	Phone number id (uuid).

Schema Changelog

Changes observed during successful MCP inspections.

First observedJul 11, 2026

TDQS

A4.2/5.0

Behavior3/5

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

No annotations are provided, so the description bears the full burden. It mentions that 'text rides in the summary' (clarifying output format) and describes long-poll behavior. However, it does not disclose auth requirements, rate limits, or whether the operation is read-only, leaving gaps.

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

Conciseness5/5

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

The description is two sentences: the first states the purpose and output fields, the second explains key parameters. No redundant wording, and essential information is front-loaded.

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?

Given no output schema, the description lists return fields (id, from_number, text, received_at) and mentions the text in summary. It covers filtering via 'match' and cursor via 'since', but lacks explicit pagination or ordering details, leaving minor gaps.

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?

Schema coverage is 100%, so the baseline is 3. The description adds value by explaining the typical use pattern for 'wait' and 'since' beyond the schema descriptions, such as 'Set wait to long-poll for new messages; use since as a cursor.'

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

Purpose5/5

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

The description clearly states 'List SMS received on a phone number' with specific fields (id, from_number, text, received_at). The verb 'List' and resource 'SMS' are explicit, and it distinguishes from siblings like 'get_sms' (single) and 'wait_for_sms' (polling only).

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?

The description explains when to use 'wait' (long-poll for new messages) and 'since' (as a cursor), providing clear usage context. However, it does not explicitly contrast with alternative tools like 'wait_for_sms' or state when not to use this tool.

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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