Sibyl

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 mentions the tool saves files but doesn't address key behavioral aspects: whether it overwrites existing files, requires specific permissions, handles errors, or has rate limits. For a file-writing tool with zero annotation coverage, this is a significant 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 appropriately sized and front-loaded: the first sentence states the core purpose, followed by usage guidance and parameter details. Every sentence earns its place with no wasted words, making it efficient and easy to parse.

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?

Given the tool's moderate complexity (2 parameters, no annotations, but with an output schema), the description is mostly complete. It covers purpose, usage, and parameters well. However, it lacks behavioral details (e.g., file overwriting, error handling). The presence of an output schema means return values don't need explanation, but other gaps remain.

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?

The description adds substantial meaning beyond the input schema, which has 0% description coverage. It explains that 'format' accepts 'pdf', 'md', or 'both' with a default, and 'output_dir' specifies the directory with a default. This fully compensates for the schema's lack of descriptions, providing clear semantics for both 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 clearly states the tool's purpose: 'Save the last research report as PDF and/or Markdown file.' It specifies the verb ('save'), resource ('last research report'), and output formats. However, it doesn't explicitly distinguish this tool from its siblings (like 'research' or 'analyze'), which would require a 5.

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 clear usage context: 'Call this after research() to save the report.' This indicates when to use the tool relative to another sibling ('research'). However, it doesn't specify when NOT to use it or mention alternatives among other siblings, which would be needed for a 5.

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