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

Annotations already cover the safety profile (readOnlyHint=false, destructiveHint=false, non-idempotent, closed-world), and the description adds real constraints beyond them: the 25-character cap on text and the YYYY-MM-DD date formats. It does not warn that repeated calls create duplicate assets (relevant given idempotentHint=false) or that a separate link call is required, which keeps it below a 5.

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?

Front-loaded one-line purpose followed by a concrete callout example, then Args/Returns. The Args list duplicates schema titles, but that duplication is justified given zero schema description coverage; the Returns block is somewhat redundant since an output schema exists.

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 an output schema present, the return-value note is a bonus rather than a requirement, and all four parameters are explained. The notable omission is the post-creation step — a callout asset must be linked via link_asset_to_campaign or link_asset_to_ad_group to have any effect, which the description only gestures at with 'can be linked'.

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%, so the description carries the full burden — and it does: customer_id 'numbers only, no hyphens', callout_text 'max 25 characters', and date formats plus optionality for both date fields. Only minor gaps remain (timezone/date semantics, whether start_date is required for end_date to apply).

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 ('Creates a callout asset') and immediately disambiguates it from the many sibling create_*_asset tools by explaining what a callout is ('short snippets of text ... e.g. "Free Shipping"'). An agent can distinguish it from create_sitelink_asset or create_text_asset without opening the schema.

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 phrase 'can be linked to campaigns or ad groups' hints at the surrounding workflow, but the description never says when to pick a callout over another asset type, nor that creation alone does not attach the asset. Usage is implied rather than stated.

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