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L5 Tools and extensions

MCP and auth

Connects outside tool servers under their own names, loads their tool descriptions only when needed, and keeps their sign-in tokens away from the model and the logs.

Settled practice

Why it matters

Outside tool servers are how most agents reach real accounts and data. Done carelessly, they flood every request with tool descriptions, let one server shadow another, and put tokens where a prompt injection or a log reader can take them.

What to build

Qualify, cap and fence every external tool name

The default the research recommends. The reasoning and the code behind it are in the app.

What it takes, by kind of agent

  • Conversational assistantMust-have
  • CodingOptional
  • Deep researchOptional
  • Browser/GUIOptional

What these levels mean

How well it is studied

Harnesses checked
30
Checked facts behind it
437

See the 437 checked facts and how each harness does it

The facts, the code lines they come from and the rules for this topic are in the app. Sign in with Google; new accounts are approved by hand.

See the evidence in the app

Also in L5 Tools and extensions

  • Code modeSettled practice

    Lets the model write one short program that calls many tools as functions inside a sandbox and returns only the final answer.

    • Assistant Optional
    • Coding Optional
    • Research Not applicable
    • Browser Not applicable
  • SkillsSettled practice

    Keeps a short list of skill names and descriptions in the prompt and loads a skill's full instructions only when the model asks for it.

    • Assistant Optional
    • Coding Recommended
    • Research Not applicable
    • Browser Not applicable
  • Planning toolsOpen problem

    Keeps a checked to-do list the agent cannot lose, and a look-only planning mode that needs the user's yes before any change.

    • Assistant Optional
    • Coding Must-have
    • Research Must-have
    • Browser Not applicable
  • Config and routingSettled practice

    Reads settings from several places in one fixed, documented order, and sends each kind of job to the model chosen for it.

    • Assistant Must-have
    • Coding Must-have
    • Research Must-have
    • Browser Must-have
  • Self-improvementEmerging

    Let the agent write its own skills and memories only under a rule, with a change log and a way back.

    • Assistant Optional
    • Coding Optional
    • Research Optional
    • Browser Optional