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

Annotations already declare readOnly/idempotent/non-destructive, so the safety profile is covered. The description adds two genuinely useful behavioral facts beyond the annotations: the required 'Authorization: Bearer <key>' header and the privacy guarantee that key values are never returned.

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, front-loaded with the returned data, then the auth requirement, then the privacy caveat. Every sentence earns its place and nothing is redundant.

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?

With no output schema, the description compensates by enumerating the returned fields (plan, rate limits, usage, key restrictions) so the agent knows what to expect. Auth requirements are stated and the privacy behavior is documented, leaving no material gap for a zero-parameter read.

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?

Zero parameters, so the baseline is 4. The description correctly implies the account is resolved from the auth key rather than any argument, adding a small amount of meaning without inventing parameter semantics that don't exist.

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+resource ('The caller's SwiftNodes plan') and enumerates the exact payload: plan, rate limits, monthly request usage, and IP/origin key restrictions. That enumeration separates it cleanly from siblings like get_pricing (catalog pricing) and get_method_support.

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 implied — an agent infers this is the tool to call to inspect its own quota and plan state — but the description never says when to prefer it over get_pricing or how it relates to the other account-adjacent siblings. No exclusions or prerequisites beyond the auth header.

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