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

Annotations already declare readOnlyHint, idempotentHint, non-destructive, and closed-world, so the safety profile is covered. The description adds a genuinely useful behavioral fact not in annotations: 'No auth required', which tells the agent this can be called before credentials exist. It does not describe return format, but annotations carry the rest.

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?

Three short sentences, zero waste, with the core purpose front-loaded and auth as the second beat. Every sentence carries new information.

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 no-param, no-output-schema read tool with rich annotations, the description covers purpose, auth requirement, and the natural next action. What a 'plan and limits' response actually contains is left implied, which is the only minor gap.

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 tool takes zero parameters, so the 4 baseline applies. The description correctly adds nothing about parameters and instead spends its words on auth and workflow context.

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?

States a specific verb ('List') and resource ('Compabase billing plans and limits'), which cleanly separates it from the singular get_plan and the mutating upgrade_plan. It does not name those siblings explicitly, so an agent must infer the distinction from plural vs singular.

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?

Gives clear sequencing context: this is a pre/post sign-up catalog read, and it explicitly routes to upgrade_plan for checkout. It does not state when to prefer this over get_plan, but the usage window is clear.

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