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

Beyond the annotations (readOnlyHint, openWorldHint, idempotentHint=false, destructiveHint=false), the description adds material context: the transport (DoH via Cloudflare 1.1.1.1), what each answer returns (TTL, response code like NOERROR/NXDOMAIN, DNSSEC verdict), pricing ($0.01/call, first 25 free, failed calls free), and that repeats are charged — which explains the idempotentHint=false. This is exactly the value-add expected when annotations are present.

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-loaded with the core action and record types, then usage, then pricing. Efficient overall, though the pricing/credits clause and 'reads or computes only' restatement add length that could be trimmed slightly.

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?

With no output schema, the description steps in to describe the returned fields (TTL, response code, DNSSEC validation), which is essential for this tool. Combined with usage routing and pricing, an agent has everything needed to call it correctly.

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%, so both parameters (name, type) and the full type list are already documented in the schema. The description restates the type list and adds a usage example (name=example.com) and the note that a URL's host is used, but that host detail is also in the schema. Baseline 3 is appropriate since the schema carries the load.

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+resource ('Look up DNS records of a domain') and enumerates the record types and returned fields, so the agent knows exactly what it does. It also distinguishes itself from the sibling dns_propagation, which handles propagation spread rather than the record lookup itself.

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 explicit use cases (check email via MX/SPF, verify a domain, debug a DNS change) and names the alternative with the condition that selects it: 'for whether the change has spread use dns_propagation'. Nothing is left to inference about when to pick this tool.

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