update_custom_fieldRename an existing custom field in SendGrid by specifying its ID and new name, so contact data definitions stay accurate and organized.
Update an existing custom field definition
| Name | Required | Description | Default |
|---|---|---|---|
| name | Yes | New name for the custom field | |
| field_id | Yes | ID of the custom field to update |
Changes observed during successful MCP inspections.
v1.1.1Input schema / additionalPropertiesRemoved value: -falsev1.0.0Input schema / $schemaAdded value: +"http://json-schema.org/draft-07/schema#"Input schema / additionalPropertiesAdded value: +falseDoes the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already declare readOnlyHint=false, idempotentHint=true, and destructiveHint=false, so the safety profile is covered by structured data. The description adds only the 'existing' target constraint and does not disclose additional behavioral details such as error behavior or effects on field values, which is acceptable but not enriching.
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 a single, tightly worded sentence with no filler. The operation and target are front-loaded, making it easy for an agent to parse quickly.
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 low-complexity tool with only two required parameters, no nested objects, and no output schema, the description plus annotations and schema cover the essential call information. Missing return-value or error expectations are minor gaps for this simple idempotent update operation.
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 field_id and name are already fully documented in the input schema. The description adds no parameter-specific meaning beyond what the schema provides, so the baseline score 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 action ('Update') and a specific resource ('an existing custom field definition'). The word 'existing' clearly distinguishes this from create_custom_field and delete_custom_field, making the tool's purpose immediately actionable.
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?
Usage is only implied through the word 'existing', which suggests this tool is for fields that have already been created. There is no explicit guidance about when to choose this over create_custom_field or delete_custom_field, and no exclusions or alternatives are named.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.