McpStamp Dunning Letters

Record that a letter was sent

letter_sent

Record that a chase letter was actually sent, with its date, so the ladder advances to the next stage. Letters go out in order: reminder 2 cannot be recorded before reminder 1. Returns what is due next and when.

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": {
      "invoice": "<invoice>"
    },
    "name": "letter_sent"
  }
}

Input Schema

Name	Required	Description
`sent`	No	The date it was sent, YYYY-MM-DD. Default today
`stage`	No	Which letter went out. Default the lowest unsent stage
`invoice`	Yes	The chased invoice: its id (DUN-2026-0001) or its invoice reference

Schema Changelog

Changes observed during successful MCP inspections.

Changed4 schema fields changedNov 6, 2026

addedInput schema / additionalProperties
```
Added value: +false
```

removedInput schema / properties / stage / anyOf

Removed value: -[
-  {
-    "const": 1,
-    "type": "number"
-  },
-  {
-    "const": 2,
-    "type": "number"
-  },
-  {
-    "const": 3,
-    "type": "number"
-  }
-]

addedInput schema / properties / stage / enum
```
Added value: +[
+  1,
+  2,
+  3
+]
```
addedInput schema / properties / stage / type
```
Added value: +"number"
```

Changed4 schema fields changedNov 6, 2026

removedInput schema / additionalProperties
```
Removed value: -false
```

addedInput schema / properties / stage / anyOf

Added value: +[
+  {
+    "const": 1,
+    "type": "number"
+  },
+  {
+    "const": 2,
+    "type": "number"
+  },
+  {
+    "const": 3,
+    "type": "number"
+  }
+]

removedInput schema / properties / stage / enum
```
Removed value: -[
-  1,
-  2,
-  3
-]
```
removedInput schema / properties / stage / type
```
Removed value: -"number"
```

First observedOct 14, 2026

TDQS

A4.2/5.0

Behavior4/5

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

Beyond the annotations, the description discloses that recording the letter advances the internal ladder and that the response returns what is due next and when. This describes the state-changing and sequencing behavior more concretely than the annotation flags alone. It does not elaborate on error behavior or idempotency, but the key side effect and return contract are transparent.

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 three sentences with no wasted words. The core purpose is front-loaded, the ordering constraint is stated in a single conditional sentence, and the response behavior is included in a short final sentence.

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 three-parameter tool with no output schema, the description covers the state transition, the ordering rule, and the response value. It could also explain what happens if the ordering rule is violated, but the overall contract is clear enough for correct invocation in most cases.

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

Parameters3/5

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

Schema coverage is 100%, so the schema already documents sent, stage, and invoice. The description adds the contextual meaning that 'stage' corresponds to ladder progression and that 'sent' is the date, but it does not introduce format or boundary details beyond the schema. This matches the baseline expected when the schema is fully descriptive.

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 states a specific action and resource: recording that a chase letter was actually sent, including its date but ignoring screen renders. It also explicitly separates this from rendering by framing it as the ladder-progression event, so an agent can distinguish it from letter_render.

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 gives clear context for when this tool should be used: when a letter physically goes out alerting the next chase stage. It also surfaces an ordering constraint—reminder 2 cannot be recorded before reminder 1—which is essential usage guidance. It does not explicitly name alternatives, but the sibling set and wording make the workflow position evident.

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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