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

Annotations already declare destructiveHint=true and readOnlyHint=false, so the agent knows this is a mutating operation. The description adds valuable behavioral context: changes take effect immediately, expected_snapshot_revision guards stale writes, and source import accepts only one source_ad_id/source_adset_id. This goes beyond the annotations and helps the agent understand side effects and concurrency protection.

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 a single dense paragraph of about 50 words. It front-loads the core action ('Update an owned template') and packs in the most important usage constraints. It's concise but slightly dense; a bit of structuring (e.g., separating the patch/update_mask note) could improve scannability, but it earns its place.

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?

Given the tool has an output schema and annotations, the description covers the key behavioral aspects: immediate effect, stale-write guard, and source import constraint. It doesn't explain return values, but the output schema exists. It doesn't mention error cases or permission requirements, but for a template update tool with this complexity, the description is reasonably 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?

Schema description coverage is 0%, so the description must compensate. It does explain the roles of template_name, template_id, new_template_name, expected_snapshot_revision, source_ad_id, and source_adset_id. However, many other parameters (tags, ad_params, adset_naming, campaign_params, etc.) are not explained in the description, and the schema itself has no descriptions. The description covers the critical parameters but not the full set, so a 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 updates an owned template, identifies the key identifier parameters (template_name or template_id), and mentions renaming via new_template_name. It distinguishes itself from templates_create, templates_delete, templates_get, templates_list, and templates_reverse_engineer by focusing on updating an existing template. However, it doesn't explicitly name a sibling alternative, so it loses a point for not explicitly differentiating from other template tools.

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 provides clear usage context: use direct fields OR patch with an exact update_mask, and expected_snapshot_revision guards stale writes. It also notes source import accepts one source_ad_id/source_adset_id. It doesn't explicitly state when NOT to use this tool or name alternatives, but the context is clear enough for an agent to know when to invoke it.

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