Generate Open Graph image

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

Annotations already declare readOnly, idempotent and closed-world, and the description usefully confirms the deterministic render contract (fixed 1200x630 PNG output from a title) and that the image itself is returned. It does not mention cost, rate limits or whether titles are truncated, but for a small pure function that is acceptable.

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?

Two tight sentences, with the core operation and output spec front-loaded and the supporting platform list second. No filler or repetition of the tool name.

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, 'Returns the image' leaves the actual return shape ambiguous (base64 payload, data URI, URL, MIME type), which matters for an agent that must consume the result. All input parameters are covered by the schema, so the gap is limited to the return contract.

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 badge, theme, footer, subtitle and title are all documented in the schema with maxLengths and examples. The description adds only that a title is the source input and the canvas is fixed at 1200x630, which is marginal beyond structured data.

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 (render), resource (Open Graph share image), exact output (1200x630 PNG) and intended consumers (X, LinkedIn, Facebook, Slack, Discord). An agent can immediately tell this generates an image rather than parsing or fetching anything like its sibling tools.

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?

The purpose line implies when to use it ('for link previews'), but there is no explicit when-not or reference to the closely named sibling get_link_preview, which is the most likely confusion point between generating a share image and retrieving a preview.

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