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

No annotations are present, so the description carries the full burden. It discloses that only passed fields are patched (not replaced), that provenance/source_* fields are immutable after save, and it explains the alias for adset_params/adgroup_params. It also reveals validation behavior for music_info. Minor omissions include return format or error handling, but the disclosed behaviors are substantial.

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 a main explanation, then REQUIRED/OPTIONAL/EXAMPLE blocks. It is compact given the amount of detail, though the phrase 'Mirrors Meta `templates_update`' adds little value and could be considered filler. Overall, each sentence 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?

For a 10-parameter mutation tool, the description covers the critical nuances: patching behavior, immutability, aliases, and a validation quirk. It does not describe return values, but with no output schema and a simple update operation, that is acceptable. It lacks explicit guidance on what happens if template_id doesn't exist, but the core usage is well covered.

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?

With schema coverage at 0%, the description lists all required and optional parameters and explains the alias relationship. It also highlights the music_info special case in ad_params. However, it does not explain the meaning or structure of the params_ objects (e.g., what campaign_params contains), leaving their semantics largely to the agent's prior knowledge. The example focuses only on tags.

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 action and resource: 'Update an existing saved template owned by the authenticated user.' It differs from siblings like templates_create, templates_delete, templates_get (read), and templates_reverse_engineer, making the tool's purpose unambiguous and distinct.

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?

It explains when to use this tool (for updates) and implicitly differentiates from create. It also gives guidance for the edge case of immutable fields, directing the agent to re-run templates_reverse_engineer to refresh them. However, it lacks an explicit exclusion statement (e.g., 'do not use for creating new templates').

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