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

Annotations already declare the write/open-world/non-destructive profile, and the description adds useful behavior: the return shape ('extension result and available identifier') and the failure modes ('validation/platform error'). The note that attachment is independent clarifies side-effect scope. It does not mention duplicate handling or permission/account prerequisites.

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 sentences: capability first, then return/error behavior and the scoping caveat. No redundant restatement of the title or parameters; every clause carries information.

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 usefully summarizes the return value and error behavior, and the scope note prevents confusion with attachment. For a simple four-required-field creation tool this is nearly complete; only account/permission preconditions 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% and all four fields carry limits (1-25 chars link text, 1-35 for descriptions), so the schema does the heavy lifting. The description only says 'using the supplied fields' without naming or explaining any of them, so baseline 3 applies.

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 — 'Create a sitelink extension in the account's Microsoft Ads asset library' — and the platform qualifier distinguishes it from create_google_sitelink_extension. The closing sentence separates it from the attach operation (add_extensions_to_native_campaign), so siblings are disambiguated.

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 establishes clear context (standalone asset-library creation, not campaign attachment) and explicitly warns that attaching is a separate operation, which prevents a common misuse. It stops short of naming the attach sibling or stating when to prefer it over creating a sitelink inline elsewhere.

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