fs_read

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

With no annotations provided, the description carries full behavioral burden and handles it well. It discloses a surprising security restriction (refuses credential stores 'regardless of principal'), which an agent could not infer from the schema, and explains truncation behavior including the result.truncated flag. This is genuinely valuable beyond the structured data.

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?

Three sentences, each earning its place: purpose first, then security refusal, then truncation behavior. No fluff, no repetition, and the most important operational constraints are packed efficiently.

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 simple two-parameter tool, the presence of an output schema, and the absence of annotations, the description covers the essential context: what it reads, what it refuses to read, and how large files are handled. Nothing critical is missing for successful 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 0%, so the description must compensate. It adds meaning to max_bytes by explaining the truncation limit and default cap. Path is self-evident and needs no elaboration. The only small gap is not explicitly stating what max_bytes=0 means, though 'or the executor's default cap' partially covers it.

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 starts with a specific verb and resource: 'Read a file's bytes as a UTF-8 string.' This unambiguously distinguishes fs_read from siblings like fs_stat (metadata), fs_search (search), and fs_list_dir (directory listing) without needing further inference.

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 intended use is clear (read file content), but there is no explicit 'when to use this vs. alternative' guidance, nor any mention of siblings like fs_stat or fs_search. The context implies usage rather than stating it, so an agent must infer routing from the name and one-liner.

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