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

Annotations already declare readOnlyHint=true and destructiveHint=false, so safety is covered. The description adds genuine value beyond that: it discloses that read scope is required and that the response includes pricing and feature limits, which tells the agent what data it will get back.

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?

Two short sentences, zero filler, with the core resource and returned fields front-loaded before the scope prerequisite. Nothing here could be cut without losing 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 zero-argument read-only tool this is nearly complete: it covers the resource, the returned fields, and the auth prerequisite, and safety is covered by annotations. The only missing piece is any hint about result shape or ordering, which is minor without an output schema.

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 no parameters, so there is no parameter semantics to explain; baseline 4 applies. The description correctly makes no attempt to describe inputs.

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 names a specific verb and resource ('get all available billing plans') and states the payload contents ('pricing and feature limits'), so an agent knows exactly what it retrieves. It doesn't need to distinguish itself from siblings because none of the listed siblings deal with billing, but it also makes no explicit differentiation.

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?

Usage is only implied: an agent can infer this is the tool for looking up plans, and 'requires read scope' gives a prerequisite. There is no statement of when to prefer it over anything else, no exclusion, and no note about whether it applies to the caller's own account or all plans.

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