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

Annotations already declare non-readOnly, openWorld, non-idempotent, non-destructive, but the description adds substantial behavior the annotations cannot convey: no account required, the 90-day/64-day lifetime caveat with a date, the CSR private-key preference, and the automatic monitoring handoff. This is rich context beyond structured fields.

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-loaded with the core action and workflow position, and every subsequent sentence carries distinct information (lifetime, challenge tradeoffs, return shape, next steps, key-handling advice). It is dense and multi-topic, bordering on long, but no sentence is filler.

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 multi-step issuance tool with an output schema present, it supplies the workflow chain, the challenge decision, the return shape (order_id plus dns_records/http_files), and the downstream tools to call. An agent has everything needed to invoke it correctly and proceed.

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 baseline is 3, but the description meaningfully expands the `challenge` parameter beyond its terse enum ('covers apex + www' vs 'issues the exact domain only') and explains the email/monitoring relationship. It says nothing about client_id or marketing_consent, so it does not fully cover the parameter set.

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?

Opens with a specific verb+resource+scope ('Start issuing a FREE Let's Encrypt certificate for a domain') and immediately positions itself as 'Step 1 of 3' in a workflow, distinguishing it from siblings like finalize_certificate and renew_certificate. An agent can tell exactly what this tool does and where it sits 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?

Explicitly states when to use each challenge mode (dns-01 for apex+www and DNS-provider automation, http-01 for a server you control on port 80) and routes the agent to the next tools ('poll check_certificate_propagation until all_found, then call finalize_certificate'). It also warns against adding a monitor manually, which is a genuine when-not-to-do-something instruction.

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