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

With no annotations, the description carries the full burden and does so well: https-only enforcement, refusal of private addresses and redirects, a 60/hour per-caller rate limit, always free, and the exact return vocabulary (flagged / no_flags / unknown) plus the critical caveat that no_flags never means 'safe'. These are exactly the operational constraints an agent cannot get from the schema.

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 dense paragraph, front-loaded with the tool's identity and trust purpose, then the mechanics and the return vocabulary. The parentheticals (https only, rate limit) each carry payload rather than filler; nothing is redundant.

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 and no annotations, yet the description supplies the return enum, the meaning of each value, the safety caveat on no_flags, the transport restrictions, and the rate limit. There is no obvious gap an agent would need to guess at before calling it.

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 both url and domain are already fully documented, making 3 the correct baseline. The description's 'Give url or domain' mildly reinforces that either form is accepted but adds no format or precedence detail beyond the schema.

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 ('checks another agent', fetches its /.well-known/agent-card.json) and frames the scope as a trust decision, which cleanly separates it from siblings like check_domain_age, check_hostname_reputation, and check_ip_abuse that a single endpoint might otherwise overlap with.

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?

'Checks another agent before you trust it' gives a clear when-to-use context, and 'Give url or domain' tells the caller what input is expected. It does not, however, explicitly name which sibling to use for narrower questions (domain age alone, hostname reputation alone) or state exclusions.

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