Read one support email in full by message ID and mark it as read, so agents can process customer requests and keep inbox status current.
Read one support email in full and mark it as read.
| Name | Required | Description | Default |
|---|---|---|---|
| message_id | Yes | ||
| justification | No | Why you are making this call, in one sentence. The person who approves it reads this; some calls need it. |
Changes observed during successful MCP inspections.
v0.13.0Input schema / properties / justificationAdded value: +{
+ "description": "Why you are making this call, in one sentence. The person who approves it reads this; some calls need it.",
+ "type": "string"
+}v0.3.8Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
With no annotations, the description carries the full burden. It usefully discloses the mutation ('mark it as read'), but says nothing about whether that write is reversible, what permissions/approval are needed, or what the read returns.
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?
One sentence, front-loaded with the action and resource, and it uses the remaining words to disclose the state change. Nothing is wasted.
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?
A mutating tool with no annotations, no output schema, and an approval-flavored justification parameter sitting alongside approval siblings (acme_check_approval, acme_ask_user). The description should at least indicate the approval/permission model and whether the read state change can be undone.
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 only 50% (message_id has no description) and the description adds no parameter meaning at all. It does not clarify the message_id format or the approval semantics of the justification field that the schema only vaguely hints at.
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?
Names a specific verb (read) and resource (one support email) plus the side effect of marking it read, which cleanly separates it from the sibling inbox_list. It does not explicitly name the alternative, but the scope distinction is unmistakable.
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: you read one message after presumably finding it via inbox_list. There is no statement of when to use this versus inbox_list or any other sibling, and no prerequisites or exclusions are given.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.