update_contact

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

With no annotations provided, the description carries the full burden. It discloses the key partial-update behavior, but omits other behavioral details such as error handling, permissions, or return value. This is better than a bare description but still leaves gaps.

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 front-loaded: 'Update fields on an existing contact' immediately states purpose. The partial-update note and example are both relevant and non-redundant. Every sentence earns its place.

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 8 parameters and no output schema. While the schema covers parameter descriptions fully, the description doesn't mention what happens if the contact doesn't exist, whether it returns the updated contact, or any validation behavior. It's adequate for basic selection and invocation but lacks some contextual richness.

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 description coverage is 100%, so baseline is 3. The description adds crucial semantic meaning: omitting optional parameters leaves them unchanged, which is not stated in the schema. The example ('Update John's phone to 555-1234') illustrates usage of the phone parameter.

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 'Update fields on an existing contact' with a specific verb and resource. It distinguishes update_contact from siblings like create_contact, delete_contact, get_contact, and list_contacts. The example adds practical clarity.

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 use when modifying an existing contact, and the partial-update note ('Only the fields you provide are changed') provides guidance on how to use optional parameters. However, it doesn't explicitly mention when not to use it or name alternative tools.

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