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

Adds real behavioral context beyond annotations: subdomain coverage (each covers its subdomains), the 500-per-call limit, and 'Sends nothing' confirming this doesn't trigger outreach. These are non-obvious operational facts not present in the annotations.

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 the purpose and scope, no waste. Every clause carries information (examples, format, subdomains, limit, no-send).

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?

Covers purpose, format, scope semantics, limits, and side-effect absence for a 2-param mutation-free tool with no output schema. Could be slightly stronger with explicit crossover guidance to unblock/list siblings.

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 already documents both parameters. The description adds value by clarifying the domains format (bare domains or URLs) and subdomain implication, but is baseline-appropriate given schema already covers params.

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?

Specific verb+resource (block domains) with the exact semantic meaning stated: domains outreach must never contact. Distinguishes clearly from sibling unblock_domains and list_blocklist by contrast.

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 the 'what and why' (competitor, partner, client - never contact) and the input format (bare domains or URLs), but never explicitly states when to use this versus alternatives like list_blocklist or unblock_domains.

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