jsonfabrica-mcp-server

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Update a JsonFabrica sequence

jsonfabrica_update_sequence

Idempotent

Update a named sequence's current value or step increment for jsonfabrica data generation. Set currentValue to reset the counter or step to change the increment; omitted fields remain unchanged.

Instructions

Calls PATCH /v1/sequences/{name}. Only the provided fields (currentValue, step) are changed; fields you omit are left as-is. Use this when you need to set an explicit currentValue (e.g. resetting a counter) or change the step amount — use jsonfabrica_bump_sequence instead when you just want to advance the sequence by its existing configured step. This overwrites the sequence's stored state in place immediately; there is no undo.

Input Schema

TableJSON Schema

Name	Required	Description
`name`	Yes	Exact name of the sequence to update. Required.
`step`	No	Changes the increment applied by future jsonfabrica_bump_sequence calls; must be a non-zero finite number (negative allowed, to count down). Optional; if omitted, the existing step is left unchanged.
`currentValue`	No	Resets the sequence's current counter value to this number, without changing `step`. Optional; if omitted, the current value is left unchanged (unless `step` is also provided, in which case only `step` changes).

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.

Changed4 schema fields changedSep 9, 2026

addedInput schema / properties / currentValue / description

Added value: +"Resets the sequence's current counter value to this number, without changing `step`. Optional; if omitted, the current value is left unchanged (unless `step` is also provided, in which case only `step` changes)."

addedInput schema / properties / name / description

Added value: +"Exact name of the sequence to update. Required."

addedInput schema / properties / step / description

Added value: +"Changes the increment applied by future jsonfabrica_bump_sequence calls; must be a non-zero finite number (negative allowed, to count down). Optional; if omitted, the existing step is left unchanged."

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?

The description adds meaningful behavioral context beyond the annotations: it states that only provided fields are changed, that the operation overwrites stored state in place, and that there is no undo. These details are not present in the annotations (which only indicate readOnlyHint=false and destructiveHint=false) and are crucial for an agent to understand side effects. No contradiction with 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 four concise sentences with zero fluff. It front-loads the endpoint and core behavior, then provides usage guidance and a warning. Every sentence earns its place, and the structure is logical and scannable.

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 mutation tool with a rich schema and an output schema, the description is complete: it covers the operation, partial-update semantics, when to use it vs. the sibling, and the irreversible nature. Nothing essential for an agent to call it correctly is missing. The output schema handles return values, so no need to describe them.

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% and each parameter has a detailed description (e.g., step explains non-zero finite requirement and negative allowed; currentValue explains resetting without changing step). The description adds a general partial-update behavior but does not add per-parameter meaning beyond the schema. Baseline 3 is appropriate since the schema carries the burden.

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 identifies the operation (calls PATCH on a sequence), specifies the fields it modifies (currentValue, step), and explicitly distinguishes it from the sibling tool jsonfabrica_bump_sequence. The verb+resource+scope is precise, making it unambiguous which tool to select.

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 gives explicit when-to-use guidance: use this tool to set an explicit currentValue (e.g., resetting a counter) or change the step amount, and directs the agent to use jsonfabrica_bump_sequence instead when only advancing by the existing step. It also clarifies partial-update semantics (omitted fields left as-is), providing clear decision criteria.

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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