fang_check_diff

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

With no annotations, the description carries the full burden. It does disclose the core mechanics (only added lines are mutated, the test suite is executed, survivors are returned), but says nothing about cost/runtime, whether the working tree must be clean, or what side effects (temp files, test execution) occur.

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?

Two sentences, front-loaded with the scoping constraint, and every clause carries information an agent needs. Nothing is padded.

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?

No output schema exists, but the description states what is returned (mutants the tests failed to detect), and all six optional params are schema-documented. It stops short of covering runtime expectations or prerequisites for a test-suite-executing tool.

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 every parameter including defaults is already documented in the schema. The description adds no syntax or behavioral nuance beyond that, so baseline 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?

States a specific verb and resource chain: mutates only added Python lines vs a git revision, runs the test suite, returns undetected mutants. The 'diff-scoped' framing implicitly separates it from fang_mutation_score (whole-project scoring), but no sibling is named explicitly.

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?

'Use this to verify that new tests actually bite' gives a clear motivating scenario, but there is no explicit when-not guidance and no routing to fang_mutation_score or fang_list_survivors for the whole-repo or follow-up cases.

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