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

Annotations already declare readOnlyHint, openWorldHint, idempotentHint, and destructiveHint. The description adds valuable context beyond annotations: 'Operator-deploy only' explains deployment dependency, and 'degrades to info when unprovisioned' describes fallback behavior. This gives the agent a clear picture of the tool's operational constraints and non-standard behaviors.

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 three sentences, each serving a distinct purpose: stating the core function, differentiating from siblings, and noting deployment behavior. No extraneous words or repetition. Information is front-loaded and easy to parse.

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?

Given the tool has 3 parameters (all documented in schema), a full output schema, and explicit annotations, the description covers all essential context: what the tool does, its niche among many sibling tools, and its deployment-dependent behavior. The description is sufficient for an agent to understand when and how to use it without consulting additional sources.

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 the baseline is 3. The description does not add new parameter-level detail beyond what is already in the schema (e.g., 'domain' and 'format' are well-described in the schema). The mention of 'Distinct from DNSBL checks' indirectly hints at the domain parameter's role but does not significantly enhance parameter semantics.

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 explicitly states the verb 'Check a domain', the resource ('BlackVeil real-time threat intelligence'), and the context ('Distinct from DNSBL checks'). It also specifies operational constraints ('Operator-deploy only; degrades to info when unprovisioned'). This clearly defines the tool's purpose and distinguishes it from sibling tools like check_rbl or check_dbl.

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 for when to use this tool: it is an alternative to DNSBL checks for real-time threat intelligence. It also mentions that it is operator-deployed and degrades when unprovisioned, which guides usage in different environments. However, it does not explicitly list when not to use it or enumerate alternatives beyond DNSBL.

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