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 clearly states the tool is 'Read-only, no side effects,' which covers safety aspects. It also describes the return format ('JSON array of {targetId, baselineScore, candidateScore, status, penalties}') and input constraints, though it doesn't mention potential errors or performance characteristics.

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 three sentences: the first states the purpose and output, the second covers behavioral traits and usage context, and the third provides exclusions. Every sentence adds value without redundancy, and key information is front-loaded.

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 tool with 2 parameters, 100% schema coverage, and no output schema, the description is largely complete. It covers purpose, usage guidelines, behavioral transparency, and parameter semantics adequately. The main gap is the lack of output schema, but the description compensates by specifying the return format. It could benefit from more detail on error cases or performance.

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 schema already documents both parameters (baseline and candidate as JSON strings). The description adds context by specifying that inputs must be 'JSON strings from analyze_url (format='json'),' which provides additional semantic meaning beyond the schema's basic type description, but doesn't elaborate on format details or validation rules.

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 with specific verbs ('Compare', 'Shows') and resources ('two Tactual analysis results'), distinguishing it from siblings like analyze_url by focusing on comparison rather than analysis. It explicitly identifies what the comparison reveals: improvements, regressions, penalty changes, and severity band changes per target.

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 ('Use after fixing accessibility issues to verify improvements') and when not to use it ('Not useful for SARIF output — use analyze_url directly for before/after SARIF comparisons'). It also specifies prerequisites: both inputs must be JSON strings from analyze_url with format='json'.

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