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

With no annotations at all, the description carries the full behavioral burden fairly well: it discloses the returned fields, states that account-specific custom plans appear only when the caller is authenticated, and implies a safe, side-effect-free read. It does not address rate limits, error behavior when unauthenticated, or whether results are paginated, which keeps it short of a 5.

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 sentences, zero filler, with the core purpose leading and the authentication caveat following. Every clause conveys information an agent would otherwise lack.

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?

There is no output schema, so the description must convey the return contents itself, and it does by enumerating credits, price, overage, and billing period. With no parameters and no annotations, the remaining behavioral surface is the auth-dependent inclusion of custom plans, which is stated.

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 parameter-semantics baseline is 4. The description correctly implies no input is required and adds nothing that could conflict with the empty schema.

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?

"List the available PDFShift plans and their pricing" names a specific verb and resource, and the parenthetical enumerates the fields returned (credits, price, overage, monthly/yearly). It does not distinguish itself from the nearby credit-related sibling credits_usage, so an agent must infer the boundary, but the purpose itself is unambiguous.

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 way to answer "what does it cost / what plans exist." The only explicit condition given is "when authenticated" for custom plans, and no alternative tool (e.g. credits_usage for consumed credits) is named or excluded.

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