check

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

No annotations are provided, so the description carries the full behavioral burden. It does disclose the return shape ('diagnostics as `renyi check --json` prints them (an empty list is clean)'), which is valuable. It does not state that the program is not executed, whether the path must already exist, or the permissions/scope required, so key behavioral context is missing.

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 dense sentences, front-loaded with the operation ('Parse, type-check and effect-check...') and followed by the parameter guidance. No filler, and the most decision-relevant information comes first.

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?

With no output schema, the description usefully explains that results are JSON-style diagnostics with an empty list meaning clean. Both parameters are covered and their interaction is explained. It stops short of covering execution semantics or error behavior, but it is adequate for a two-parameter read-only 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 coverage is 100%, so the baseline is 3, but the description adds genuine meaning: it clarifies that the two parameters are alternative inputs and that `path` doubles as the module name for import resolution when `source` is given. That relationship is not evident from the schema alone, so it exceeds the baseline.

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 specific verbs and resource: 'Parse, type-check and effect-check a program and report its diagnostics.' That is far more specific than the bare name 'check' and implies a static-analysis operation, distinguishing it in spirit from siblings like run and format. It stops short of explicitly contrasting itself with siblings such as effects or run_tests, so it is clear but not fully differentiated.

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?

It gives concrete guidance for choosing between `path` and `source`, including that `path` names the file for import resolution when `source` is supplied. However, it never says when to use this tool rather than alternatives like `run`, `run_tests`, or `effects`, which are the likely confusions given static-checking versus execution. Usage is implied rather than stated.

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