validate_vast_url

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

Annotations already provide readOnlyHint=true and destructiveHint=false, indicating it's a safe read-only operation. The description adds behaviors like handling redirects and auto-detecting formats, which is beyond the annotation. However, it does not detail the output structure beyond validation, and the output schema may carry that. It could be more transparent about network failures or error handling, but given the annotations, the description adds some value, not a lot.

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?

The description is compact, about three sentences, each providing distinct value: what it does, format support, and usage guidance. It is front-loaded with the primary action and ends with usage context. No fluff or redundancy.

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 two parameters, full schema coverage, an output schema present, and annotations indicating a safe read operation, the description covers the essential context. It mentions formats, redirect handling, and depth control. The only minor gap is not specifying error behavior when the URL is invalid or network issues occur, but for this tool's simplicity, the description is nearly complete.

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?

The schema description coverage is 100%, meaning both parameters (url and max_depth) are already documented in the schema. The description adds that max_depth controls wrapper chain depth and default is 5, which is a slight extension but essentially repeats the schema. It doesn't add substantial new meaning; therefore, baseline 3 is appropriate.

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 clearly states the tool's purpose: fetching and validating an IAB ad tag XML from a URL. It specifies the accepted formats (VAST 2.0-4.4, VMAP 1.0, DAAST 1.0/1.1) and distinguishes from siblings like 'inspect_vast' and 'fix_vast' by focusing on fetching and validating, not inspecting or fixing. This makes it distinct and clear.

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 description explicitly tells when to use this tool: 'AI agents typically receive VAST URLs rather than raw XML — use this tool for that case.' This is direct usage guidance. It also mentions the max_depth parameter and its default, which helps in deciding how to configure the call. There is no explicit mention of when not to use it, but the 'use this tool for that case' strongly implies usage context, which is effective guidance.

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