Create an index

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

The description adds a valuable behavioral detail beyond the annotations: the operation fails rather than overwriting when the index already exists. This complements the annotations, which already indicate a non-read-only, non-idempotent write operation. It does not elaborate on all side effects, but the conflict behavior is the key operational trait.

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 two sentences with no filler. It leads with the core action, then immediately states the failure condition and the correct alternative. Every sentence serves a distinct purpose and the structure makes it easy to scan.

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?

The description, together with the fully documented schema and annotations, provides enough context for correct invocation: required parameter, optional mapping/settings parameters, and the failure mode. It does not mention the create_index_template sibling, but that is not essential for invoking this specific tool correctly.

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?

All three parameters are already documented in the input schema, including examples for mappings and settings, so schema coverage is 100%. The description does not add additional parameter-level meaning, but it does not need to; the schema carries that burden effectively.

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 action and resource: 'Create a new index.' It also differentiates itself from the closest sibling, create_mapping, by explicitly saying to use that tool for adding fields to an existing index. The purpose is immediately clear and not a tautology.

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 explicit when-to-use guidance: use this tool for creating a new index. It also gives an explicit when-not-to-use and alternative: 'Fails if it already exists — use create_mapping to add fields to an existing one.' This leaves little ambiguity about which tool to select.

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