add_contact

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

Annotations already indicate a write operation (readOnlyHint=false), so the description doesn't need to state that. It adds a useful constraint (user must exist) and a privacy-related behavioral note about add_phone_privacy_exception. However, it does not disclose side effects, reversibility, or auth requirements beyond what annotations provide.

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 concise and uses a clear bullet-list format for parameters. It is front-loaded with the main action, but the omission of required parameters is a structural flaw that costs it a perfect score.

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, 2 of which are required, and the description misses the required first_name. It also lacks context about return values, error conditions, or behavior when adding an already-existing contact. The description is inadequate for reliable invocation.

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?

The description explains the meaning of user, phone, and add_phone_privacy_exception, but it completely omits first_name and last_name, even though first_name is required by the schema. With schema description coverage at 0%, this is a critical gap that leaves the agent unable to correctly fill required parameters.

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's action with a specific verb ('Добавить' = Add) and resource ('пользователя в контакты' = user to contacts). It distinguishes from sibling tools like delete_contact, import_contacts, and block_user by specifying the singular, direct action of adding a single contact.

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 specifying the prerequisite that the user must already exist ('существующего юзера'), but it does not explicitly state when to use this tool versus alternatives like import_contacts or send_contact. No exclusions or alternative recommendations are provided.

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