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

Annotations already declare readOnlyHint=true and openWorldHint=false, so the safety profile is clear. The description adds useful behavioral context beyond annotations by explaining that binary files are returned base64 encoded and that the encoding appears on the first line.

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 definition is short and front-loaded: the core purpose is stated first, followed by the important binary-return caveat. The docs link adds negligible bulk and does not obscure the key information.

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 read-only tool with a fully described two-parameter schema and no output schema, the description is nearly complete: it explains the binary return encoding, which is the main non-obvious behavior. Minor gaps remain around error behavior for missing files, but they are not essential for correct invocation.

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 both parameters are already documented in the input schema. The description reinforces that the call targets one companion file but does not add syntax or format details beyond the schema's path example.

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 uses a specific verb and resource: read one companion file of a skill. It distinguishes itself from get_skill by focusing on a companion file, though it does not explicitly name sibling alternatives such as list_skill_files or get_skill.

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 implied by 'Read one companion file of a skill': call it when you need the contents of a specific known file. There is no explicit when-to-use guidance, no mention of using list_skill_files to discover paths, and no when-not-to-use exclusions.

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