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

With no annotations, the description carries the full burden of disclosing behavior. 'AST-valid write' and 'replace' indicate mutation and AST preservation, but the description does not disclose side effects, file persistence, error behavior, reversibility, or validation details. For a write tool, this is a significant transparency gap.

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 a single, focused sentence with no filler. It front-loads the tool's nature ('Small AST-valid write') and then gives the two usage modes clearly. It could be slightly more structured, but it earns its length.

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?

The tool has 7 parameters, no annotations, and no output schema, yet the description is quite brief. It omits the required file_path semantics, optional node_kind/column behavior, return values, error behavior, and relationship to sibling tools. This is insufficient for an agent to use the tool confidently in varied situations.

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 only 14%, so the description must compensate. It usefully explains the symbol_name + new_implementation pairing and the line + new_source pairing, but it leaves file_path, column, and node_kind unexplained. The description adds some meaning beyond the schema but does not fully cover all parameters.

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 states a specific verb and resource ('AST-valid write') and gives two concrete modes: replacing a symbol or replacing the node at a line. This makes the tool's purpose reasonably clear, though it does not explicitly distinguish it from siblings like hexum_expand or hexum_shrink.

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 no guidance on when to use hexum_splice versus its sibling tools. It only explains internal parameter modes ('Pass symbol_name + new_implementation... or line + new_source...'), which is not the same as selecting the right tool among alternatives.

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