◒ ToolCapsule
MCP tools as lightweight Agent Skills

Heavy MCP tools don’t belong in your prompt.

ToolCapsule keeps schema-heavy MCP servers out of the context window by turning them into lazy-loaded, file-first Agent Skills with patch-and-retry recovery.

View on GitHub npm i -g toolcapsule tcap tools feishu --brief
88.4% fewer input tokens
87.6% fewer total tokens
100% planning success rate

The problem

MCP made tools universal. It also made tool context heavier.

Native MCP is excellent for small, frequent tools. But document and workflow MCP servers often expose long descriptions, schemas, and rules that can be visible to the model even when the user is only planning.

ToolCapsule keeps MCP as the capability layer and uses Skills as the agent-facing workflow layer. Full schemas are still available, but no longer need to be carried every turn.

The capsule

A tool call becomes a patchable artifact.

Instead of asking the model to regenerate a large tool call after a failure, ToolCapsule stores the arguments, payloads, request, response, and error as local files.

runs/2026-06-06T10-00-00
args.json
content.md
request.json
response.json
error.txt
command.txt
01

Discover briefly

List MCP tools as compact summaries instead of injecting every schema.

02

Write locally

Put Markdown, JSON, and long arguments into files the agent can patch.

03

Call deterministically

Run the MCP tool through a CLI and save the full request/response trace.

04

Patch and retry

Fix the local file and replay the same tool call without rewriting the prompt.

Native MCP

Regenerate the call

  • Tool schemas stay close to the prompt.
  • Large payloads are reassembled by the model.
  • Retries can accidentally change correct content.

ToolCapsule

Patch the artifact

  • Schemas are lazy-loaded when needed.
  • Payloads live in args.json and content files.
  • Retries are auditable, local, and deterministic.

For heavy MCP servers

Keep the protocol. Change the workflow.

ToolCapsule is designed for Feishu/Lark, Notion, Jira, Linear, Confluence, GitHub management tools, and internal SaaS MCPs.

Start with ToolCapsule