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

With no annotations, the description carries the full behavioral burden and does a solid job: it discloses the sandboxed Docker execution model, the third-party API dependency, a 30-second wall-clock limit, and a 512MB RAM ceiling. It stops short of stating auth requirements, rate limits, or whether submitted code or artifacts are persisted, which are meaningful gaps for a remote execution tool.

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?

Four short sentences, front-loaded with the core action and environment, then constraints and return values. Sentence two partly restates sentence one, and the return-value sentence duplicates information already available in the output schema, so a small amount of the text does not earn its place.

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 three-parameter execution tool with an output schema and no annotations, the description supplies the operational constraints an agent actually needs (sandbox, timeout, memory ceiling). The remaining omission is the dependency on list_compilers for valid compiler IDs, which is covered in the schema rather than the prose.

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 code, input, and compiler, including the example compiler IDs and the pointer to list_compilers. The description only echoes that stdin is optional and that a compiler must be specified, adding no syntax or format detail beyond the structured fields, so the baseline of 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?

The description names a specific verb and resource ('Execute code') and pins down the execution environment ('sandboxed Docker container via the OnlineCompiler.io API'), which no sibling could plausibly share. The only sibling, list_compilers, is a discovery helper, and the phrase 'the specified compiler' implicitly signals that a compiler identifier must be obtained first, so an agent can tell the two apart without opening a schema.

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?

Usage is only implied: an agent infers 'use this when you need to run code,' but there is no explicit statement of when to prefer this tool, when not to use it, or that list_compilers should be called first to obtain a valid compiler identifier. The routing hint for the sibling lives in the schema's compiler parameter, not in the description.

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