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

With no annotations, the description carries the full behavioral burden. It does disclose a concrete behavioral trait — a cost of 1 credit per call — which is genuinely useful. However, it omits other important traits: what happens when no snapshot exists, whether the call fails or returns the nearest available, and what a successful result contains.

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?

A single compact sentence that leads with the core action and follows with the optional parameter and cost note. No filler, every clause contributes 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 two-parameter tool with no output schema and no annotations, the description covers the action, the optional date, and cost, which is the minimum viable set. It still leaves the return shape (snapshot URL? timestamp?) and the no-snapshot edge case unspecified, which an agent would want before calling.

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 50%: `url` is documented but `date` has only a regex pattern. The description compensates by explaining the date as YYYYMMDD and, more importantly, clarifying that a date selects the *closest* snapshot rather than requiring an exact match. Minor tension: the schema pattern allows 4–14 digits while the description specifies 8.

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 gives a specific verb and resource ('Find the closest archived snapshot of a URL in the Internet Archive') and adds the key scope qualifier that it returns the *closest* snapshot, not a full history. It is clearly distinguishable from siblings like crawl_site or page_metadata, though it does not explicitly name any alternative.

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 rather than stated: an agent can infer this is the tool for retrieving archived versions of a page, and the optional date hints at point-in-time retrieval. There is no when-not guidance, no mention of alternatives (e.g. crawl_site for live content), and no stated behavior for URLs with no archive.

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