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

Beyond the readOnlyHint/destructiveHint annotations, it discloses that no credential is needed, that it reads the snapshot the running deployment was built from rather than a live repository, and that server routes are deliberately excluded. It also explains the revision semantics and why base_rev must match the file's sha256, which materially changes how an agent should use the result.

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?

Every sentence earns its place: listing mode, read mode, snapshot guarantee, revision contract, and route exclusion are all consequential. The most important scoping information is front-loaded in the first sentence.

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?

Even without an output schema, the description tells the agent what each call returns, how to map the digest into propose_change, and what files are off-limits. There are no obvious gaps an agent would need before calling this tool correctly.

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 single optional path parameter, and the description adds meaningful behavior: no path lists all files with size and sha256; a path returns bytes, digest, and rev. It also connects the returned sha256 to the base_rev of propose_change, going beyond the schema.

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 states a specific verb (read) and resource (this site's own writable source) and explicitly ties it to propose_change, so an agent knows this is the source-of-truth reader for files it may modify. The title 'Read the code you are allowed to change' further differentiates it from sibling readers like read_sources by emphasizing the writable, deployment-bound scope.

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?

It gives clear call context: use before propose_change, omit path to list every changeable file, provide a path to read a specific file, and expect server routes to be absent. It stops short of naming alternative tools explicitly, so there is no explicit when-not-to-use comparison, but the context is strong.

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