Frida Agent MCP

Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

With no annotations provided, the description carries the full burden. It discloses key behavioral traits: the script is wrapped with try-catch for safety, the tool returns immediately after injection (asynchronous behavior), and results must be retrieved via get_messages(). However, it doesn't mention potential side effects like application instability or permission requirements.

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 efficiently structured with a clear purpose statement upfront, followed by behavioral details, and then parameter explanations. Every sentence adds value: the first states what it does, the second explains safety wrapping, the third clarifies async behavior and result retrieval, and the parameter section provides practical guidance.

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?

Given the tool's complexity (code injection into running applications) and lack of annotations, the description does well by explaining the async nature, safety mechanism, and parameter usage. However, it doesn't mention potential failure modes or security implications. The presence of an output schema means return values don't need explanation, but more behavioral context would be beneficial.

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 0%, so the description must compensate fully. It provides clear semantic meaning for both parameters: 'script' is Frida JavaScript code with guidance to 'Use send() to return data', and 'script_file' is a path to a .js file for large scripts. The description adds essential context beyond the bare schema.

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 clearly states the specific action ('Inject a Frida JavaScript script') and target ('into the frontmost application'), distinguishing it from siblings like 'spawn_and_inject' (which likely spawns a new process) or 'connect' (which establishes connection). The verb+resource combination is precise and unambiguous.

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 explicitly states when to use this tool ('Returns immediately after injection - use get_messages() to retrieve results after the user has triggered the target functionality') and provides a clear alternative for large scripts ('Use this for large scripts instead of script parameter'). It also distinguishes from siblings by specifying it targets the 'frontmost application'.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.