Create or update an index template

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

Annotations already indicate a mutating, idempotent, non-destructive operation. The description adds important behavior beyond the annotations: the Elasticsearch 7.8+ requirement and the non-retroactive nature of the template. No contradiction exists between description and annotations.

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?

A single sentence communicates the action, resource, version constraint, and the most important behavioral caveat with no filler. The key scoping limitation is front-loaded and easy to parse.

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 write tool with 5 parameters, a nested template object, and no output schema, the description covers the decisive behavioral constraint and version compatibility while relying on the fully documented schema for parameter details. It does not mention the response format, but that is a minor gap for a create/update tool.

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%, so all five parameters already have inline documentation. The description does not add substantial parameter-level meaning beyond the schema, making the baseline 3 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 states a specific verb ('Create or update') and a specific resource ('composable index template'), which clearly distinguishes it from sibling tools like create_index or create_mapping. The version qualifier and 'applies only to indices created after it' add further precision about what the tool does.

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 gives clear context: this tool is for defining templates that affect future indices only, and it explicitly states it never affects existing indices. It does not name alternative tools for existing-index changes, but the exclusion is clear enough for an agent to reason about when to use it.

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