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

Annotations already declare readOnlyHint=true, so the description does not need to repeat that. The description adds useful behavioral context: it returns full file contents and that these contents are the exact text to match against for apply_changes edits. It also discloses the 20-file limit, which is a functional constraint beyond the schema. This adds meaningful context without contradicting annotations.

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 two sentences with zero fluff. It front-loads the primary purpose and the key constraint (20 files), then provides a practical reason for the return value. Every sentence earns 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?

The tool has an output schema (indicated by context signals), so return-value details are covered there. The description covers the essential usage constraints (20 files, relative paths, full contents) and the apply_changes matching context. It does not discuss error conditions or edge cases, but for a read-only tool with a simple interface, this is adequate. It slightly misses explicitly contrasting with read_file, but that is not critical for completeness.

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% for the two parameters, so the schema already documents their meaning and constraints. The description does not add additional parameter-level detail beyond what is in the schema; the mention of 'up to 20' is already in the file_paths description. Since the schema carries the weight, a baseline score of 3 is appropriate.

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 a specific action ('Read up to 20 files from a project in one call') and the resource. However, it does not explicitly differentiate from the sibling tool 'read_file' (singular), though the name and the 'up to 20' limit imply the distinction. It is clear but lacks explicit sibling differentiation.

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 implies usage by mentioning that the returned text is what 'apply_changes' matches against, suggesting a primary use case. However, it does not explicitly state when to use this tool versus alternatives like 'read_file', nor does it mention any exclusion conditions. The guidance is only implied through the apply_changes context.

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