Domain details

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

Annotations already cover safety (readOnlyHint, idempotentHint, destructiveHint false), so the description adds value by clarifying the current-snapshot scope, the single-domain constraint, and the categories of data returned. It does not cover potential caveats like caching or rate limits, but these are minor for a read-only lookup.

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 sentences with no wasted words. The core action and return contents are front-loaded, and the usage recommendation is appended as a single compact sentence.

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 tool with two well-documented parameters, safety annotations, and no output schema, the description adequately summarizes what the caller receives: current DNS record types, hostname counts, and registrar metadata. The response_format behavior is already captured in the schema, so nothing essential 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% and both parameters (domain and response_format) already have clear descriptions with format, default, and enum constraints. The tool description adds only the 'one domain' context, which is useful but does not meaningfully expand on the schema's parameter documentation.

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 names a specific verb ('Fetch'), a concrete resource (DNS records, hostname counts, registrar metadata), and explicitly enumerates the record types included. The phrase 'current DNS records' distinguishes it from the sibling securitytrails_dns_history, making the tool's role unmistakable.

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 statement 'The best first call when profiling an unfamiliar domain' gives an explicit, actionable use case and positions this tool early in a workflow. It does not name alternatives or explicitly state when not to use it, so it stops short of full routing guidance.

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