agent4.io

update_skill

Update part of a skill — fields you don't pass stay as they are (server-side PATCH merge, no GET+PUT round-trip).

⚠️ `tools=[...]` is **full-list replacement**; to add/remove one use `add_tools`/`remove_tools`
(incremental, idempotent). Tools bound to a skill take effect automatically at chat time on any
agent the skill is attached to — no need to also add them to the agent's tools.

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": {
      "name": "<name>"
    },
    "name": "update_skill"
  }
}

Input Schema

Name	Required	Description	Default
`name`	Yes
`tools`	No
`add_tools`	No
`description`	No
`instructions`	No
`remove_tools`	No

Output Schema

Name	Required	Description	Default
`result`	Yes

Schema Changelog

Changes observed during successful MCP inspections.

Changed2 schema fields changedJul 30, 2026

addedInput schema / properties / add_tools

Added value: +{
+  "anyOf": [
+    {
+      "items": {
+        "type": "string"
+      },
+      "type": "array"
+    },
+    {
+      "type": "null"
+    }
+  ],
+  "default": null,
+  "title": "Add Tools"
+}

addedInput schema / properties / remove_tools

Added value: +{
+  "anyOf": [
+    {
+      "items": {
+        "type": "string"
+      },
+      "type": "array"
+    },
+    {
+      "type": "null"
+    }
+  ],
+  "default": null,
+  "title": "Remove Tools"
+}

First observedJul 28, 2026

TDQS

A4.7/5.0

Behavior5/5

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

With no annotations provided, the description carries full responsibility for behavioral disclosure. It clearly discloses PATCH merge behavior ('fields you don't pass stay as they are'), the full-list replacement nature of tools, the incremental/idempotent nature of add_tools/remove_tools, and the automatic propagation to agents. This is comprehensive.

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 concise yet dense: one sentence for core PATCH behavior, one focused warning block for tools replacement. It is front-loaded with the primary purpose and contains no filler.

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?

With an output schema present, return values are covered. The description fully addresses the key operational nuances (merge semantics, tool replacement, incremental add/remove, and automatic agent effect) making it complete for a tool of this complexity. Missing aspects like error handling are not necessary for the description to be complete.

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 description coverage is 0%, so the description must compensate. It adds crucial semantics for tools-related parameters (tools full-list, add_tools/remove_tools incremental). However, it does not elaborate on description or instructions parameters beyond their obvious names, leaving those to schema field names only.

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 opens with 'Update part of a skill' which is a specific verb+resource, and further clarifies the semantics with 'server-side PATCH merge, no GET+PUT round-trip.' This distinguishes it from a full update tool and from the sibling create_skill, making the purpose unmistakable.

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?

It provides explicit within-tool guidance: 'tools=[...] is full-list replacement; to add/remove one use add_tools/remove_tools' and explains that bound tools automatically affect agents. However, it does not explicitly contrast with create_skill or other sibling update tools, relying on the name for that distinction.

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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