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

With no annotations, the description carries the full burden and does disclose key traits: read-only, keyless (no auth), and critically 'Reads Tranco's database, never the target' — an important disclosure that it does not touch the scanned domain. It omits rate limits, caching, or data-freshness caveats, keeping it short of 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 the purpose in the first clause, then layers interpretation value. Every sentence earns its place — the phishing-tell and scrutiny framing are directly actionable, and there is no filler.

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 must explain return values, and it does (rank, band, daily-list count). For a one-parameter read tool, 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 description coverage is 100% with a single trivially-named 'domain' parameter, so the schema already fully documents the input. The description adds no input syntax or format guidance beyond what the schema provides; 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 ('Report a domain's popularity on the Tranco research list') and enumerates the return units (rank, band, daily-list appearance count). This is distinguishable from every sibling (typosquat_scan, blacklist_check, related_domains) 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 clear framing for when the result matters ('a cheap context signal', 'a top-1k domain and an unranked one warrant very different scrutiny', 'an unexpectedly unranked lookalike is a phishing tell'). However, it never names a specific sibling alternative to use instead or an explicit exclusion, so it falls short of the 5 bar.

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