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

With no annotations, the description carries the full burden and does reasonably well: it discloses the auth requirement (ogs_ key), the billing model (one credit per image), that the result is hosted and stable, and a negative constraint ("Does not return a free hotlink"). It stops short of describing failure modes, image retention, or rate limits beyond credits.

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?

Four short sentences, front-loaded with the core action and return value, with no filler. The final sentence ("Does not return a free hotlink") is slightly cryptic and would benefit from sharper wording, but it does convey a real constraint.

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?

There is no output schema, so the description correctly spends words on the return value (the hosted PNG URL). Combined with 100% schema coverage and stated auth/cost, an agent has enough to call it correctly; only persistence and error behavior are 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 100% with 13 well-described params including 4 enums, so the schema already does the heavy lifting and a baseline of 3 applies. The description adds no parameter-level detail beyond restating that api_key is required and costs a credit, which the schema already says.

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?

The description uses a specific verb plus resource ("Build a hosted Open Graph PNG") and even states the return artifact (a stable https://ogstamp.com/i/{id}.png URL for og:image), which is more than most definitions offer. It does not explicitly contrast itself with the sibling og_image_from_url, so the agent must infer the params-vs-URL distinction from the names alone.

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?

Prerequisites are stated (api_key from the pricing page, one credit per image), which implies the cost/auth context for use. However, there is no explicit when-to-use guidance and no mention of when to prefer the sibling og_image_from_url or og_pricing, so the routing decision 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.