Encrypt a plain-text message with AES-256-CBC using a passphrase key, applying scrypt key derivation and a fresh random IV for each call.
Encrypts a message
| Name | Required | Description | Default |
|---|---|---|---|
| message | Yes | The message to be encrypted | |
| encryptionKey | Yes | The key used for encryption |
| Name | Required | Description | Default |
|---|---|---|---|
| encryptedMessage | Yes | The encrypted message (format: iv:ciphertext) |
Changes observed during successful MCP inspections.
v0.0.1Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
No annotations are provided, so the description carries the full behavioral burden, and it discloses almost nothing: no cipher/algorithm, key format or length expectations, output encoding, or error behavior for invalid keys. The existence of an output schema excuses explaining return values, but the operational behavior is undocumented.
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 single four-word sentence is front-loaded and wastes nothing, but its brevity reflects under-specification rather than disciplined conciseness given the cryptographic complexity involved.
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 security-sensitive two-parameter required-input tool with zero annotations, the description should at least mention key requirements and output form. The output schema covers return values, but the description leaves the operation's constraints entirely unstated.
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%, with both 'message' and 'encryptionKey' documented in the schema itself. The description adds no additional meaning (e.g., key format or size), so the baseline of 3 applies.
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?
"Encrypts a message" states a specific verb and resource, and the encrypt/decrypt pairing with the sibling is inferable. However, it is essentially a restatement of the tool name with no added scope or distinguishing detail.
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?
No guidance on when to use this tool versus decrypt_message, and no prerequisites such as whether the caller must already possess a key. Usage is only implied by the name.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.