set_auth

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

No annotations are provided, so the description carries the full burden. It discloses that cookies are stored at a specific path (/root/.carsales-mcp/cookies.json), and that the action enables authenticated operations. It does not explicitly state overwrite behavior or validation, but the intended effect and storage location are clear.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Is the description appropriately sized, front-loaded, and free of redundancy?

The description consists of two dense sentences with no wasted words. It front-loads the purpose, then provides the storage path and a practical sourcing suggestion. Every sentence adds value.

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

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

For a single-parameter tool with no output schema, the description is surprisingly complete. It explains what the tool does, why it matters, where cookies are stored, and how to construct the input. No essential context is missing for an agent to call it correctly.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

The schema already covers the parameter, but the description adds valuable guidance on how to obtain the cookies (from DevTools > Application > Cookies or a cookie export extension). This goes beyond the schema's generic description and directly instructs the agent on the format and source of the value.

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

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

The description clearly states the tool's purpose: importing a login session via cookies, with the specific benefit of enabling authenticated actions like saving vehicles and making offers. It distinguishes itself from sibling auth_status by its direct action (setting vs. checking) and is specific about the resource (carsales.com.au session).

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

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

The description implies when to use it (when you need authenticated access to carsales) and even explains the underlying purpose (so the server can save vehicles, make offers, contact sellers). However, it does not explicitly mention alternatives like auth_status or state when not to use it, leaving the routing partially implicit.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.