set_contact_field

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

With no annotations provided, the description carries the behavioral disclosure burden. It explicitly says 'Write: overwrites the stored value,' which tells the agent this is a mutating operation and that the prior value is replaced. It does not cover permissions or error behavior, but it discloses the most important side effect.

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 deliberately compact: one sentence for the action, one for parameter sources, and one for the write behavior. Every clause earns its place and the most important information is front-loaded.

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?

For a three-string-parameter setter with no nested objects and no output schema, this description provides the operation, parameter sourcing, and mutation semantics. It is adequate for an agent to invoke correctly, though it leaves success/error behavior and permission requirements unspecified.

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 0%, so the description must compensate. It usefully identifies the provenance of two otherwise bare string parameters ('user_ns from find_contact', 'field_name from list_contact_fields') and the overwrite behavior implies that 'value' is the new field value. This adds real meaning beyond the minimal schema.

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 ('Set') and resource ('custom field on one contact'), making the operation immediately clear. It does not explicitly compare against siblings like add_contact_tag or list_contact_fields, but the custom-field wording is enough to separate it from the tag and listing tools in the sibling list.

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 gives clear working context by telling the agent where to source parameters: 'user_ns from find_contact' and 'field_name from list_contact_fields'. It does not explicitly state when not to use it or name alternatives, but the preconditions are concrete enough for correct selection and sequencing.

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