add_contact

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

No annotations are provided, so the description carries the full behavioral burden, yet it says nothing about authentication requirements, duplicate-contact handling, or what happens on a number already in contacts. For a mutation tool with zero annotation coverage this is a real gap.

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?

A single short sentence with the action front-loaded and no filler. Its brevity is efficient, though it shades into under-specification rather than optimal conciseness.

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?

A zero-parameter, no-output-schema, no-annotation tool that nonetheless claims a phone-number input leaves the calling contract ambiguous. The description does not close that gap, so an agent cannot reliably invoke it.

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?

With zero parameters the baseline would be 4, but the description asserts the contact is added "by phone number" while the schema declares no properties, leaving the agent unsure how the phone number is actually supplied. That mismatch between stated input and structured schema is a semantic gap, not added value.

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 states a specific verb + resource ("Add a contact") and adds a discriminator ("by phone number") that separates it from siblings like import_contacts or add-by-username tools. It is clear but stops short of explicitly contrasting with import_contacts/contacts siblings.

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?

No when-to-use, when-not-to-use, or alternative routing is given, even though the sibling list contains import_contacts, contacts, and delete_contact that an agent must choose between. The implied distinction from bulk import is left entirely to inference.

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