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

Annotations indicate readOnlyHint=false (it creates), destructiveHint=false (non-destructive), and openWorldHint=true. The description does not contradict these; it consistently describes a creation operation. However, it adds minimal behavioral context beyond what the annotations imply—no mention of side effects, permissions, or response format. Given the annotations already establish the safety profile, a 3 is appropriate; the description adds context about what a callout is but not deeper behavioral details.

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 well-structured with clear headings, front-loading the core definition, then providing usage guidance and examples. It is somewhat verbose with sections for keywords and 'ALSO KNOWN AS', but these aid in natural-language matching. Every section serves a purpose, and it is not bloated with irrelevant details.

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 a single parameter, no output schema, and no nested objects, the description is fully sufficient for an agent to call the tool correctly. It explains what the tool does, when to use it, when not to use it, and describes the sole input with an example. Nothing critical is missing.

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% (the schema already defines callout_text with min/max lengths). The description adds semantic value by labeling it as a 'visible snippet' and providing examples of valid callout text ('Free Shipping', '24/7 Support'). This helps the agent understand the intended content type beyond the raw schema definition.

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 function: adding a non-clickable selling-point snippet (callout) beneath Microsoft Ads. It provides concrete examples of callout text and explicitly distinguishes itself from sibling extensions (sitelink, structured snippet). The verb 'Add' and resource 'Microsoft Ads Callout Extension' are specific, and it is clearly differentiated from the Google and Microsoft variants.

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 has dedicated 'WHEN TO USE' and 'WHEN NOT TO USE' sections with concrete example user queries and explicit exclusions. It names alternative tools (create_microsoft_sitelink_extension, create_microsoft_structured_snippet_extension, create_google_callout_extension) and the conditions that should route an agent to them. This leaves no ambiguity about when to invoke this tool.

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