create_gsi

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

The description discloses that 'Index creation is asynchronous — use describe_table to monitor progress', a critical behavior beyond the annotations. It also notes the prerequisite that 'The table must be in ACTIVE status' and states the return value confirms initiation. This adds meaningful context beyond the structured annotations, though it could mention potential delays or failure modes.

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-organized into a main paragraph, explicit 'When to use'/'When NOT to use' sections, and a 'Returns' line. Every sentence earns its place, with no redundant content. It is concise yet complete.

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 output schema and annotations, the description covers essential context: the table's required status, async behavior, monitoring via describe_table, and alternative conditions. It fully equips an agent to decide when and how to invoke the tool, and the return type is stated. No major gaps are apparent.

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?

The description does not enumerate any parameters (table_name, index_name, partition_key, etc.), leaving that to the schema. The schema's top-level 'input' parameter has 0% description coverage, but nested properties are well-described. The description adds conceptual context (e.g., 'non-primary-key attributes') but does not explicitly connect parameters to usage, so it only partially compensates for the low coverage.

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 'Create a Global Secondary Index (GSI) on a DynamoDB table' with a specific verb and resource. It also explains that GSIs enable querying on non-primary-key attributes, distinguishing it from table creation and other sibling tools like create_table or describe_table.

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 includes explicit 'When to use' and 'When NOT to use' sections, providing concrete conditions such as 'To enable queries on attributes that aren't part of the primary key' and 'If a suitable GSI already exists (check with describe_table first)'. It also names describe_table as an alternative for monitoring and pre-checking.

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