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

Annotations already declare destructiveHint=true, idempotentHint=false and openWorldHint=true, so the risk profile is known without the prose. The description adds genuine context beyond that by framing the call as a full replacement ('all record fields must describe the desired replacement'), warning the agent that omitted settings are not preserved. It does not spell out that unset optional fields (ttl, priority, port, weight) fall back to schema defaults, nor mention DNS propagation delay.

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?

Three short sentences, no filler, with the replacement semantics and the list_dns_records prerequisite both front-loaded. Every sentence carries distinct information: what it does, what to do before calling, and how to build the payload.

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?

Output schema exists and annotations are rich, so return values and safety are covered elsewhere. However, a nine-parameter destructive mutation with 0% schema coverage and no enum constraint on record_type leaves real gaps: accepted record types, TTL units/bounds, and when record_port/record_weight/record_priority are applicable (only MX and SRV) are all unaddressed.

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 carry parameter meaning, and it covers essentially one field: dns_zone_record_id, including where to source it from list_dns_records. The other eight parameters — domain, record_name, record_type, record_value, record_ttl, record_priority, record_weight, record_port — get only the collective phrase 'all record fields'. Notably, record_type is a free string with no enum, so supported record types (A, AAAA, CNAME, MX, SRV, TXT) need to come from somewhere and the description does not supply them.

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 and resource ('Replace an existing managed DNS record'), which separates it from add_dns_record and delete_dns_record among its siblings. The line 'All record fields must describe the desired replacement' implicitly distinguishes it from a partial-update tool like configure_dns_record, but that sibling is never named, so the differentiation is left to inference.

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 an explicit precondition and workflow: 'Call list_dns_records first and pass its DNS zone record ID.' That is concrete, actionable guidance an agent can follow directly. It stops short of naming when to prefer this over configure_dns_record or add_dns_record, so the alternative-selection guidance is incomplete.

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