jsonfabrica-mcp-server

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Bump a JsonFabrica sequence

jsonfabrica_bump_sequence

Advance a named sequence by its configured step, permanently updating its current value and returning the updated record for use in synthetic data generation.

Instructions

Calls POST /v1/sequences/{name}/bump. Atomically advances the sequence by its configured step (a permanent, irreversible change to the stored currentValue) and returns the updated record — this is the same advance a template's createSeq()/getSeq() calls trigger during generation. Use jsonfabrica_update_sequence instead if you need to set an explicit currentValue/step rather than advancing by the existing step.

Input Schema

TableJSON Schema

Name	Required	Description	Default
`name`	Yes	Exact name of the sequence to bump (advance by its configured step). Required.

Output Schema

TableJSON Schema

Name	Required	Description
`name`	Yes	Sequence name.
`step`	No	Increment applied per bump (ignored for "uuid").
`type`	Yes	Value kind produced on each bump.
`start`	No	Initial value the sequence was created with.
`tenantId`	Yes	Owning tenant id.
`createdAt`	Yes	ISO-8601 creation timestamp.
`updatedAt`	Yes	ISO-8601 last-update timestamp.
`currentValue`	Yes	Current stored counter value (unused by "uuid" sequences).

Schema Changelog

Changes observed during successful MCP inspections.

Changed2 schema fields changedSep 9, 2026

addedInput schema / properties / name / description

Added value: +"Exact name of the sequence to bump (advance by its configured step). Required."

changedOutput schema / (root)

Previous value: -nullNew value: +{
+  "$schema": "http://json-schema.org/draft-07/schema#",
+  "additionalProperties": false,
+  "properties": {
+    "createdAt": {
+      "description": "ISO-8601 creation timestamp.",
+      "type": "string"
+    },
+    "currentValue": {
+      "description": "Current stored counter value (unused by \"uuid\" sequences).",
+      "type": "number"
+    },
+    "name": {
+      "description": "Sequence name.",
+      "type": "string"
+    },
+    "start": {
+      "description": "Initial value the sequence was created with.",
+      "type": "number"
+    },
+    "step": {
+      "description": "Increment applied per bump (ignored for \"uuid\").",
+      "type": "number"
+    },
+    "tenantId": {
+      "description": "Owning tenant id.",
+      "type": "string"
+    },
+    "type": {
+      "description": "Value kind produced on each bump.",
+      "enum": [
+        "number",
+        "string",
+        "uuid"
+      ],
+      "type": "string"
+    },
+    "updatedAt": {
+      "description": "ISO-8601 last-update timestamp.",
+      "type": "string"
+    }
+  },
+  "required": [
+    "tenantId",
+    "name",
+    "type",
+    "currentValue",
+    "createdAt",
+    "updatedAt"
+  ],
+  "type": "object"
+}

First observedv0.1.4Sep 5, 2026

TDQS

A4.7/5.0

Behavior5/5

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

Beyond annotations (readOnlyHint=false, idempotentHint=false), the description discloses atomicity ('Atomically advances'), irreversibility ('permanent, irreversible change'), and the return behavior ('returns the updated record'). It also connects to template generation behavior, adding valuable operational context not present in annotations.

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, front-loaded with the core action and endpoint, then the alternative. No wasted words; every clause adds value. The structure is exemplary for a tool definition.

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

Completeness5/5

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

For a simple one-parameter tool with an output schema, the description fully covers purpose, when to use, behavior, and alternative. It omits return format (handled by output schema) and prerequisites (implied by sequence existence). Nothing an agent needs to call it correctly is missing.

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?

The input schema already provides 100% coverage, describing 'name' as the exact sequence name and marking it required. The description adds only that the name is used in the URL path, which is a minor clarification. With full schema coverage, baseline 3 is appropriate.

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 the tool advances a sequence by its configured step, specifies the HTTP endpoint (POST /v1/sequences/{name}/bump), and explicitly differentiates it from the sibling jsonfabrica_update_sequence which sets explicit values. This is specific verb+resource and distinguishes from alternatives.

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

Usage Guidelines5/5

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

The description explicitly tells when to use this tool vs the alternative: 'Use jsonfabrica_update_sequence instead if you need to set an explicit currentValue/step rather than advancing by the existing step.' It also adds context that this matches what createSeq()/getSeq() trigger, giving a clear decision heuristic.

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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