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

Annotations already establish readOnlyHint, idempotentHint, and non-destructive behavior, so the bar is lower. The description adds useful behavioral context beyond annotations: line-based pagination via offset/limit and support for both text and binary files. This gives the agent a meaningful picture of how the tool returns 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 short sentences with zero filler. The primary use case is front-loaded, followed by return behavior and capabilities. 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?

For a read-only tool with rich annotations, the description covers the essential facts: what it reads, what it returns, how pagination works, and the text/binary behavior. It does not explain potential error cases or exactly how binary content is encoded, but those are minor given the simple use case and schema coverage.

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%, and the schema already documents app_id, file_path, offset, limit, and version in sufficient detail. The description only reinforces the pagination concept already visible in the schema, so it does not add meaningful semantic value beyond the structured fields.

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 a specific file') and a specific resource ('an app's source snapshot'). It does not explicitly name sibling tools like src_glob or src_grep for differentiation, but the 'specific file' phrasing makes the scope understandable without opening the 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?

'Use this when you need to read a specific file from an app's source snapshot' gives a clear invocation context. It does not explicitly mention when not to use it or name alternatives such as src_glob or src_grep, so it falls short of the top score but is still clear.

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