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

With no annotations provided, the description carries the full burden of behavioral disclosure. It reveals key side effects: automatic inverse relationship creation/update/removal, the requirement to use a prime tool ID for self-relationships, and the acceptance of custom relationship_type values from Settings. These insights go beyond the schema and help the agent understand the tool's consequential behavior. However, it omits permissions, reversibility, or response format, so a 4 is appropriate rather than 5.

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-structured with bullet points for each action, making it easy to scan. The opening sentence states the core purpose, and each bullet contains essential information without fluff. It is slightly verbose due to repeating action prefixes, but every sentence earns its place, so a 4 is warranted rather than 5.

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 description covers all four actions, required parameters, inverse behavior, self-contact handling, and relationship types. For a tool with this complexity (4 actions, 6 parameters) and no output schema, it is largely complete. Minor gaps like error conditions or response format do not significantly impact usability, but given the lack of annotations, a 4 is fitting.

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?

While the schema already documents all 6 parameters with 100% coverage, the description adds action-specific parameter semantics (e.g., which params are required for each action) and clarifies that notes are optional for add/update. It also explains that relationship_type includes canonical values plus custom values, enriching the parameter meaning beyond the schema's description. This added value justifies a 4, above the baseline of 3.

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 opens with a specific verb+resource: 'Add, update, remove, or list relationships between contacts.' It clearly defines the tool's scope and distinguishes it from sibling tools (e.g., contact_update, tag_manage) by focusing on relationships. The example 'Bandit is Bingo's parent' further clarifies the semantic intent, 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 offers detailed action-specific guidance, listing required parameters for each action (add, update, remove, list). It also includes a specific instruction for creating relationships involving yourself ('use your own contact_id from the prime tool'). While it doesn't explicitly compare with alternative tools, the action breakdown provides clear when-to-use context, earning a 4.

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