Update a contact property's fallback value to set a new default or clear it. Use this to change the default value for existing contacts without altering the property key or type.
Update a contact property's fallback value (PATCH /contact-properties/:id). key/type are immutable.
| Name | Required | Description | Default |
|---|---|---|---|
| id | Yes | The contact property id. | |
| fallback_value | No | New default value (pass null to clear). |
Changes observed during successful MCP inspections.
v1.0.2Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
No annotations are provided, so the description alone must disclose behavior. It clearly states the operation (PATCH update) and the immutability constraint, which is valuable. However, it does not disclose potential side effects (e.g., overwriting existing values), required authentication/permissions, or what happens if the property does not exist. The description meets the baseline but leaves notable gaps for a mutation tool.
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 one tight sentence that front-loads the action, resource, and field, with the HTTP method in parentheses and the immutable constraint appended. There is zero filler, and every word 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?
For a two-parameter PATCH tool with no output schema and no annotations, the description is nearly sufficient: it tells the agent what to update, that key/type cannot be changed, and the HTTP endpoint. It could additionally mention error conditions or ownership requirements, but for the tool's simplicity, these are minor omissions. A score of 4 reflects the high signal-to-noise ratio.
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%; both 'id' and 'fallback_value' are already documented in the schema, including the 'pass null to clear' behavior. The description adds little parameter-specific meaning beyond the HTTP method and immutability constraint, which are contextual rather than semantic. Baseline of 3 is appropriate.
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 ('Update'), a specific resource ('a contact property's fallback value'), and even includes the HTTP method (PATCH /contact-properties/:id). It clearly distinguishes this from create/delete/get/list contact property tools by noting key/type are immutable, so an agent can identify its scope without opening the schema.
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 implied usage context: it is for updating the fallback value, and key/type cannot be changed here. However, it never explicitly names the alternative (e.g., 'use create_contact_property to set key/type') or states when this tool should not be used. The immutability note implies the boundary but stops short of clear guidance.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.