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

Annotations already cover the safety profile (readOnly, non-destructive, openWorld), and the description adds real substance on top: result ordering, the fields returned, that DNSSEC keys are omitted, the 500-per-page cap, and the underlying GET /domains/ endpoint. This is meaningful context beyond the structured hints.

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 core purpose and scope, then layers ordering/fields, the sibling pointer, the parameter guidance, the page limit, and the endpoint. Every sentence carries information and nothing is redundant.

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 still describes the return shape (creation time, last-published time, minimum TTL) and pagination behavior (cursor, up to 500 per page), while annotations cover the read-only/open-world profile. 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 coverage is 100%, so the schema already documents both parameters (baseline 3). The description nonetheless adds interpretive value by explaining the intent behind owns_qname (longest matching zone you own) and giving a motivating example, going past what the schema's own text conveys.

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 (List) and resource (DNS domains/zones) scoped to 'this deSEC account', plus ordering ('newest first') and returned fields. It explicitly distinguishes itself from the sibling desec_get_domain by naming where DNSSEC keys live, so an agent can route without opening the schema.

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?

Provides a concrete when-to-use for the owns_qname parameter ('find which of your domains is responsible for a DNS name... before adding a record for www.dev.example.net') and redirects to desec_get_domain for the omitted DNSSEC keys. Clear context, though it doesn't state when NOT to list (e.g. single-domain lookups beyond the DNSSEC case) with the same precision.

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