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

Annotations already declare readOnly, idempotent, and openWorld=false, so the safety profile is covered. The description adds real behavioral context beyond them: the empty-list-instead-of-error contract for non-DST zones and the $0.05 x402/USDC payment requirement, both of which materially affect invocation.

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?

Front-loaded with the core purpose and return shape, and each clause carries information (offsets, jump direction, DST state, next transition, empty-list behavior, price). The pricing sentence is somewhat tangential to selection but is genuinely useful for a paid tool.

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 takes on return-value disclosure and does so thoroughly (transition instants, offsets, jump direction, current state, next transition). It also covers the payment model, so an agent has everything needed to call 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?

Schema coverage is 100%, so the schema already documents zone, from, and years including accepted formats and defaults. The description adds essentially no syntax or format detail beyond the schema, so the baseline of 3 applies.

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 (daylight-saving transitions) with explicit output content: shift instants, before/after offsets, and jump direction. An agent can distinguish this from siblings like time_zone or time_calendar without opening the schema.

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 by the scoping ('over a date range', 'from a given instant') but there is no explicit when-to-use guidance or routing to/away from alternatives such as time_zone. The empty-list edge case is stated, but no conditions for choosing this tool over siblings are given.

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