domain_add_subdomain

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

Annotations only declare it is a non-read-only, non-destructive mutation; the description adds substantial hidden behavior: Beget auto-creates A/MX/TXT(SPF) records, the name resolves to shared hosting before any user A-record, and MX/SPF silently survive dns_set_a. This is exactly the kind of side-effect disclosure an agent cannot get from 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?

Front-loads the purpose, then the input constraint, then the critical side-effect warning — a logical progression. The warning paragraph is long but every clause carries load-bearing information about records that would otherwise surprise the caller.

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 mutation tool, the safety profile is covered by annotations, the output schema covers return values (and the description even flags the records field), and both parameters are fully explained. Nothing needed to invoke it correctly 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 0%, so the description must compensate, and it does: it specifies that subdomain is a prefix only (blog, not blog.site.ru), that the value will be rejected otherwise, and that domain_id carries the parent with a pointer to domain_list. Both parameters gain meaning beyond their bare schema titles.

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 (create a subdomain) and scopes it precisely: the subdomain must be a bare prefix, not an FQDN. It distinguishes itself from domain_add (creates domains) and domain_subdomains (lists them) by naming the parent-vs-child relationship.

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?

Requires an existing parent and points to domain_list for resolving domain_id, giving clear usage context. It stops short of naming alternatives or exclusions, but there is no competing sibling that creates subdomains, so the guidance is nearly complete.

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