Plan a free TLS certificate

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

Annotations already cover the safety profile (readOnlyHint, idempotentHint, destructiveHint=false), and the description adds genuinely new context: the certificates:read permission requirement, the explicit guarantee that no certificate is issued and no DNS is modified, and that only currently available choices are returned. It stops short of describing failure modes (e.g., ineligible hostname) or rate limits, so it is strong but not exhaustive.

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 sentences, zero filler, and the ordering: purpose first, then return shape, then the call-this-before instruction. Every sentence carries distinct information an agent needs.

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 usefully enumerates what comes back (canonical names, validation, delivery, key-custody and CA options) and states the prerequisite permission. What is missing is behavior on ineligibility or unavailable options, and any pointer to eligibility-checking siblings, so it is nearly complete rather than fully so.

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 hostname, alternative_names, target_order_id, and certificate_authority are already fully documented in the schema. The description only echoes the CA-choice and name concepts at a high level, adding no syntax or format detail beyond the structured fields — the baseline 3 applies.

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 ('Plan a no-cost public DV certificate') plus the critical scope boundary 'without issuing it or changing DNS.' An agent can immediately distinguish it from create_free_certificate, which is the adjacent write tool.

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 sequencing ('Call this before create_free_certificate') and an operating instruction for the result ('follow only options marked available'), which names the alternative and the condition that routes to it. Nothing about when to reach for this versus the create tool is left to inference.

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