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

Annotations already declare readOnlyHint=true, destructiveHint=false and openWorldHint=false, so safety is covered. The description adds a genuine behavioral constraint not present in annotations: attempts to read outside the home are refused, which tells the agent the sandbox is enforced server-side rather than validated by the caller.

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 clauses with the main operation and scope front-loaded, and no wasted preamble. The final sentence about a path beginning with the home's own name is dense and slightly redundant with the parenthetical, but it is not filler.

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 2-parameter read tool with annotations covering safety, the definition covers scope and boundary enforcement. With no output schema, it leaves unstated what reading returns (file contents? encoding? size limits?), which matters for a tool whose name is read_file.

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 50%: home_path is well documented in the schema, while relative_path has no schema description. The description partially compensates by defining relative_path as relative to the home and by noting that an address beginning with the home's own name resolves inside the home, though that last clause is ambiguous rather than clarifying.

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?

Names a specific verb (read) and resource (one file) plus the scoping constraint that the path is relative to a home, which separates it from read_home and update_home_file. It does not name a sibling outright, so differentiation is inferential rather than explicit.

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 read-only framing and the refusal of out-of-home paths imply when this tool applies, but there is no explicit when-to-use guidance versus read_home (whole-home view) or raw_source. The agent must infer the boundary from the requirement to supply both home_path and relative_path.

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