Update a custom property's name, type, or values. Use null to keep existing values, or an empty array to clear them.
Update a Custom Property. values=null → unchanged; values=[] → removes all values. Requires 'Write' on 'CustomProperty'.
| Name | Required | Description | Default |
|---|---|---|---|
| id | Yes | ||
| name | No | ||
| typeId | No | ||
| values | No | ||
| typeName | No |
Changes observed during successful MCP inspections.
v1.0.0Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
With no annotations provided, the description carries the full behavioral burden. It discloses the auth requirement and the non-obvious semantics of values=null versus values=[], which are not visible in the input schema. It does not mention reversibility, return value, or error behavior, so it is not a perfect 5, but it is far more transparent than a bare 'update' statement.
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?
Three short sentences, each earning its place: the purpose statement, the critical values behavior, and the permission requirement. There is no filler or restating of schema fields, and the most important update trap is front-loaded right after the purpose.
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 description covers the most important usage gotchas (values null vs []) and the auth requirement, which is essential for calling the tool correctly. However, the behavior of the other updatable fields (name, typeId, typeName), partial-update semantics, and the return payload are all unaddressed. With no output schema and no annotations, those gaps leave an agent partially guessing.
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 input schema has 0% description coverage, so the description must compensate. It adds meaningful, non-obvious semantics for the values parameter: null means unchanged and [] removes all values. However, it provides no guidance for name, typeId, or typeName, leaving those parameters only as raw schema names. This partial compensation warrants a mid-range score.
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 'Update a Custom Property,' which names a specific verb and resource. The values=null vs values=[] distinction adds precise scope, and the tool's name clearly differentiates it from sibling add/delete/search tools without needing their schemas.
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 makes the operation context unambiguous: it is for updating an existing custom property. It also gives a permission precondition, 'Requires Write on CustomProperty.' It does not explicitly enumerate when-not-to-use or name alternatives, but the sibling set (custom_properties_add, custom_properties_delete, etc.) makes the boundary clear.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.