Create a resource proof

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

Annotations only declare the safety profile (non-read-only, idempotent, non-destructive, open-world). The description adds real behavioral context the annotations don't: the call blocks until Lob renders the proof, bounded by LOB_PROOF_WAIT_MS, and returns render_pending: true when still rendering. That renders-safe, returns-something-unfinished nuance is valuable and non-obvious.

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, front-loaded with the resource definition before the usage caveat. Dense and mostly waste-free; the caveat sentence is long but carries routing value.

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?

No output schema exists, so the description correctly carries the return-value burden by explaining the render_pending fallback and the blocking window. Combined with the sibling-routing note, an agent has enough to call and interpret 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 description coverage is 100%, so the schema already documents all four parameters. The description's note that resource_parameters mirrors the underlying create endpoint's shape (with examples) adds mild provenance context but little beyond the schema, so the baseline of 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?

Specific verb+resource: 'Create a proof — a PDF preview of how a resource (postcard, letter, self-mailer) will print.' It defines the artifact precisely and its role in the mail workflow, clearly distinguishing it from the create/send siblings.

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 it ('for review before committing to a mail send') and, more importantly, when not to: it names that the lob_*_preview tools call this endpoint internally and that the raw tool is for advanced use cases, routing the agent to the simpler alternative.

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