athena_explain_join

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

Discloses outputs (join cols, confidence, warnings, SQL snippet) and mentions specific warnings (CONTEXTID, multi-tenant security). No annotations exist, so description carries full burden; it could note whether the operation is read-only or if it modifies state, but 'explain' implies read.

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?

Two sentences with no fluff: first sentence states purpose and output, second sentence provides critical usage guidance. Every word 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?

Given no annotations, no output schema, and two simple string parameters, the description covers what the tool does, what it returns, and when to use it. Could mention prerequisites (e.g., views must exist), but overall sufficient for an agent to select and invoke 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?

Both parameters (sourceView, targetView) have full schema coverage with descriptions and examples in the description text. The examples ('APPOINTMENT', 'DEPARTMENT') add clarity beyond the schema.

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 it explains join between two views, listing specific outputs (join columns, confidence, warnings, SQL snippet). This verb+resource combination is distinct from siblings like athena_explain_view which handles single views.

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?

Explicitly advises 'Always call this before writing a JOIN to avoid silent data loss from incorrect key usage.' This provides clear when-to-use and a strong consequence for not using the tool.

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