opensearch_discover_fields

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

With no annotations provided, the description fully carries the burden of behavioral disclosure. It reveals key traits: only returns fields that appear in sampled documents, fields absent won't be listed, requires search privilege, and sample_size max 100. It could be more explicit about the trade-off of small sample sizes leading to incomplete results, but overall it provides sufficient behavioral context.

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 only three sentences, each serving a distinct purpose: stating the primary use case, explaining a key limitation, and comparing with a sibling tool while giving actionable advice. No words are wasted, and the most important information is front-loaded.

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 presence of an output schema, the description does not need to detail return values. It covers purpose, usage, behavioral traits, and parameter guidance. It could mention that the index must exist or how errors are handled, but for a relatively simple tool, it is highly 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 100%, so baseline is 3. The description adds some context around sample_size by suggesting increasing it for broader coverage and mentioning the max of 100. However, it does not add significant new meaning beyond what the schema already provides for other parameters.

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 explicitly states the tool's purpose as a fallback for opensearch_get_mapping when the mapping API is blocked, and that it samples live documents to discover fields. It clearly distinguishes itself from the sibling tool opensearch_get_mapping, making the purpose unambiguous.

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 explicitly tells when to use this tool (as a fallback when the mapping API is blocked) and why it is preferred in certain contexts (only requires search privilege). It also provides guidance on adjusting sample_size for broader coverage, giving clear usage recommendations.

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