join

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

Annotations declare readOnlyHint=true, and description confirms 'Read-only, no side effects'. Adds context about output format (JSON) and the necessity of sorted input. Could mention max_lines or performance limits, but overall transparent.

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?

Five concise sentences, front-loaded with core purpose and constraints. No wasted words. Well-structured for quick understanding.

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?

Despite no output schema, description mentions JSON output. Covers key preconditions, alternatives, and warnings. Could detail output structure, but adequate for a standard join tool given sibling context.

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 provides 100% coverage with descriptions. The description adds context about default join field and pre-sorting, but does not elaborate on individual parameters. Baseline of 3 is appropriate as schema handles documentation.

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 the tool joins two sorted files on a common field (default: first whitespace-separated field), performing an inner join. It distinguishes from similar tools like paste and comm, 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?

Explicitly states requirement for pre-sorted input and warns against unsorted input. Provides alternatives ('use sort first', 'use paste' for side-by-side merging). Clear when-to-use and when-not-to-use guidance.

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