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

Annotations already declare readOnlyHint=false and idempotentHint=true, so the description doesn't need to restate that this is a write operation. The description adds value by explaining the semantics of each relation type and the single/bulk modes, but it doesn't disclose behaviors like whether existing links are overwritten, whether items must exist, or what happens on duplicate attempts. With annotations covering the core safety profile, this is adequate but not enriched.

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, front-loaded with the primary action, and every phrase earns its place: the first sentence lists the relation types with brief definitions, and the second sentence covers both invocation modes. No filler or redundancy.

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 tool has 5 parameters, no output schema, and annotations. The description covers all parameter semantics, explains the relation enums, and distinguishes single vs bulk usage, which is sufficient for an agent to invoke it correctly. Minor gaps like return behavior or error handling are not explicitly mentioned, but the annotation set and schema provide good context, making this fairly 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 coverage is 100% (every parameter has a description in the schema), so baseline is 3. The tool description adds meaningful semantics beyond the schema by explaining the enum values with parentheticals (e.g., 'alternative (A or B)', 'upgrade (B replaces A)') and clarifying how 'pairs' relates to bulk mode versus individual from_id/to_id/relation. This extra context pushes it above baseline.

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 uses a specific verb ('Create') and clear resource ('typed relations between items'), enumerates the exact relation types (alternative, complement, upgrade, duplicate, same_seller), and distinguishes this tool from siblings like unlink_items and add_to_collection by focusing on typed relational links rather than generic collection membership.

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 implies usage by showing two modes (single pair and bulk) and explains the meaning of each relation type, but it does not explicitly state when to use this tool versus alternatives, nor does it mention exclusions like 'use unlink_items to remove relations'. The context of creating links is clear, but no explicit when/when-not guidance is provided.

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