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

Annotations already cover the safety profile (readOnlyHint, idempotentHint, destructiveHint=false), so the bar is lower; the description still adds ordering (newest first), temporal coverage (1996 to current crawl), and a full enumeration of returned capture fields. It omits rate limits and pagination behavior (limit/offset semantics live only in the schema), 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?

Front-loads purpose, then return fields, then accepted inputs, then sibling routing. Four dense sentences with no filler, though the field-enumeration sentence is long and could be trimmed since it partially overlaps the schema's implicit return contract.

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?

No output schema exists, so the description correctly compensates by enumerating returned fields (timestamp, replay URL, status, MIME, length, digest, text/raw/screenshot links). Combined with URL formats, date range, ordering, and sibling routing, nothing an agent needs to call it correctly is missing.

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 documents all five parameters and baseline is 3. The description adds real meaning for the required 'url' param by specifying accepted forms (bare domain, host, or full URL with path/query), which the schema only illustrates by example.

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 ('List every preserved capture of a specific URL in Arquivo.pt'), scopes it ('newest first — the version history of a page or domain from 1996 to the current crawl'), and explicitly distinguishes from siblings arquivo_page_text and arquivo_search_pages. An agent can select this 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?

Gives explicit when-to-use ('see how a Portuguese page changed over time or to find the capture timestamp to pass to arquivo_page_text') and an exclusion with the alternative ('use arquivo_search_pages when you only know words from the page, not its address'). Clear conditional routing to two siblings.

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