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

Annotations already declare readOnly, idempotent, openWorld and non-destructive, so safety is covered. The description adds genuinely useful behavior beyond that: it discloses that results are a triple of closest/first/latest snapshots rather than an arbitrary list. It says nothing about rate limits or lookup failures, keeping 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 tight sentences, front-loaded with what the tool does and what it returns, followed by when to reach for it. No filler or repetition of the name.

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?

An output schema exists, so return-shape explanation is unnecessary, and the annotations carry the safety profile. With only two fully documented parameters and explicit usage triggers, an agent has everything needed to select and invoke it 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 description coverage is 100%, so the schema already documents both url and date with accepted formats. The description's 'closest to a date' reinforces the date parameter's intent but adds no syntax or edge-case detail beyond the schema, so baseline 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 and resource ('Find Wayback Machine snapshots of a page') and enumerates exactly what is returned: the snapshot closest to a date, the first capture, and the latest. The 'archived' framing cleanly separates it from live-fetch siblings like read_url and inspect_source.

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 situational triggers ('when a page was deleted or edited', 'to see what it said at a point in time', 'to check how long it has existed'). It stops short of naming an alternative tool or an explicit when-not-to-use condition, so it is strong context rather than full routing guidance.

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