mcp-server-cloudflare

cf_kv_put

Store data in Cloudflare KV by writing values to specified keys within a namespace. Use this tool to manage key-value storage for Cloudflare Workers applications.

Instructions

Write a value to KV

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": {
      "namespaceId": "<namespaceId>",
      "key": "<key>",
      "value": "<value>"
    },
    "name": "cf_kv_put"
  }
}

Input Schema

Name	Required	Description
`namespaceId`	Yes	KV namespace ID
`key`	Yes	Key to write
`value`	Yes	Value to store
`accountId`	No	Account ID

Schema Changelog

Changes observed during successful MCP inspections.

First observedv1.0.1Mar 10, 2026

TDQS

C2.9/5.0

Behavior2/5

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

With no annotations provided, the description carries the full burden of behavioral disclosure. It states 'write' which implies a mutation, but doesn't cover critical aspects like whether this overwrites existing values, requires specific permissions, has rate limits, or what happens on success/failure. This leaves significant gaps for safe tool invocation.

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 extremely concise at just four words, with zero wasted language. It's front-loaded with the core action and resource, making it easy to parse quickly. Every word earns its place.

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

Completeness2/5

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

Given the complexity of a write operation to a key-value store with no annotations and no output schema, the description is inadequate. It doesn't explain what the tool returns, error conditions, or behavioral traits like idempotency. For a mutation tool with 4 parameters, more context is needed for reliable use.

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 description coverage is 100%, so the schema fully documents all parameters (namespaceId, key, value, accountId). The description adds no additional meaning beyond the schema, such as explaining parameter relationships or constraints. The baseline of 3 is appropriate since the schema does the heavy lifting.

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

Purpose4/5

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

The description 'Write a value to KV' clearly states the action (write) and resource (KV/key-value store), distinguishing it from sibling tools like cf_kv_get (read) and cf_kv_delete (remove). However, it doesn't specify that this is for Cloudflare KV specifically, which could help differentiate from generic KV tools.

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

Usage Guidelines2/5

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

The description provides no guidance on when to use this tool versus alternatives like cf_kv_get or cf_kv_delete, nor does it mention prerequisites such as needing a namespace ID or account ID. It lacks context about typical use cases or constraints.

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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