tactual-mcp

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

With no annotations provided, the description carries the full burden of behavioral disclosure. It effectively describes key behaviors: 'Overwrites the output file if it already exists,' 'Writes a storageState JSON file to disk,' 'Launches a headed browser that interacts with the page,' and includes detailed step format examples. However, it doesn't mention potential failure modes or error handling.

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 well-structured with clear sections: purpose, side effects, usage guidance, and parameter details. It's appropriately detailed for a complex tool but could be slightly more concise by reducing some repetition in the examples. Every sentence adds value.

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 complex authentication tool with no annotations and no output schema, the description does an excellent job covering purpose, usage, parameters, and behavioral context. It explains what the tool does, when to use it, how parameters work, and what happens during execution. The main gap is lack of information about return values or error conditions.

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 the baseline is 3. The description adds significant value by explaining the complex 'steps' parameter format with detailed examples and clarifying the relationship between 'outputPath' and sibling tools. This goes well beyond what the schema provides, though it doesn't add much for simpler parameters like 'timeout'.

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 tool's purpose: 'Authenticate with a web application and save the session for subsequent analysis.' It specifies the verb (authenticate and save), resource (web application session), and distinguishes from siblings by focusing on authentication rather than analysis or remediation.

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 provides explicit guidance on when to use this tool: 'Not needed for public pages — only use when content is behind authentication.' It also specifies how to use the output with sibling tools: 'Pass the output file path as `storageState` to analyze_url, trace_path, or analyze_pages to analyze authenticated content.' This clearly differentiates it from alternatives.

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