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

Annotations already declare readOnlyHint=true and openWorldHint=false, so the safety profile is covered; the description still adds real value by disclosing the hard 3-item cap, the 'NEVER returns the full feed' truncation behavior, and the rationale (context budget protection). It does not say what happens if the feed has never been served or is stale, nor whether a refresh is required first — a meaningful omission for a verification tool.

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 tight sentences with the core behavior and the 3-item scope front-loaded, followed by the rationale and the escape hatch. Every clause earns its place: 'exactly what Meta / Google would see' conveys fidelity that would otherwise take a paragraph.

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 does identify the return content as feed XML (first 3 items), which is the key thing an agent needs. Remaining gaps are secondary but real: it does not state the response envelope (raw XML string vs structured object) or error behavior for an unknown feedId.

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 0% for the single parameter, so the description carries the burden of explaining feedId, and it says nothing about it. The name is self-explanatory and consistent with sibling tools, but there is no statement about where feedId comes from or what happens with an invalid/missing one, so this is only baseline-adequate.

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 with an explicit scope: it returns the first 3 items of the served feed XML, described as 'exactly what Meta / Google would see'. The purpose (verifying filterRules + fieldRules + outputSchema output) is unambiguous. It does not, however, differentiate itself from the sibling preview_render tool, which an agent may reasonably consider for the same verification task.

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?

It gives an explicit when-to-use (verify filterRules, fieldRules and outputSchema produce the right output) and an explicit when-not-to-use / alternative for the full output (the dashboard or /api/serve/[feedId]). The hard limit of 3 items is framed as a constraint rather than a surprise, so the agent knows exactly which tool to pick for which need.

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