blacklist_checkCheck if a domain or IP address is listed in popular email blacklists (DNSBLs). Being blacklisted can severely impact email deliverability.
| Name | Required | Description | Default |
|---|---|---|---|
| domain_name | Yes | The domain name or IP address to check against blacklists, e.g. example.com or 1.2.3.4 |
Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
The description states the core behavior (checking blacklists) and adds context about email deliverability impact. With strong annotations (readOnlyHint=true, idempotentHint=true), the description doesn't need to repeat safety traits. It adds no additional behavioral details like rate limits or response format, so it meets the baseline but doesn't exceed it.
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?
The description is two sentences, front-loaded with the action, and every word contributes. The second sentence provides useful rationale without being verbose.
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 simple one-parameter tool, the description adequately explains the purpose and context. However, since there is no output schema, the description could have mentioned what the tool returns (e.g., a list of blacklists or a boolean), which would make it more complete. This is a minor gap.
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% since the only parameter has a description. The description does not add any new information about the parameter beyond what the schema already provides. It follows the baseline for high schema coverage.
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 uses a specific verb 'Check' and identifies the resource 'domain or IP address' and the context 'listed in popular email blacklists (DNSBLs)'. This clearly distinguishes it from sibling tools like dns_lookup or spf_check, which have different purposes.
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?
The description provides clear context by mentioning 'being blacklisted can severely impact email deliverability', implying it should be used when troubleshooting email deliverability. However, it does not explicitly name alternatives or state when not to use this tool compared to other DNS-related checks.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.
Add one secure layer between your agents and this server.
Each tool has a specific purpose, but dns_lookup overlaps with cname/mx/ptr/txt lookups since it returns all record types. The 'check' tools validate records while 'lookup' tools merely retrieve them, which helps differentiate, but an agent could still confuse e.g., txt_lookup with dkim_check.
Naming follows a noun_action pattern (e.g., bimi_check, mx_lookup) but uses inconsistent actions: check, lookup, finder, and generate. 'imap_finder' and 'smtp_finder' break the noun_verb pattern, and there is no uniform verb choice.
With 16 tools, the count is at the upper edge of reasonable for an email deliverability domain. The individual DNS checks and server tests are justified, but some consolidation (e.g., a single lookup tool with record type parameter) could reduce redundancy.
Covers critical authentication checks (SPF, DKIM, DMARC, BIMI), blacklist checks, DNS lookups, and SMTP/IMAP connection tests. Missing DKIM generation and deeper reputation tools, but core deliverability verification is well-covered.