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

Annotations already cover read-only, idempotent, non-destructive semantics, and the description adds meaningful operational context beyond them: each call is metered as one execution, short results return inline within ~2 seconds, and otherwise the returned IDs feed operation_status/operation_output with an explicit 'do not resend the call' instruction. This materially shapes how an agent should behave.

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 dense sentences with the usage trigger front-loaded and no wasted framing. The async-result sentence is long but each clause (metering, inline vs. deferred, do-not-resend) carries distinct information.

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?

With no output schema, the description correctly explains the return model (inline vs. ID-based retrieval) and the metering/auth prerequisites. It omits guidance on the optional deadlineAt and efficiencyProfile parameters and on error or binary-file cases, leaving minor gaps for an eight-parameter tool.

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%, so the schema already documents all eight parameters including line ranges and the deadline/operationId semantics. The description adds little parameter-level detail beyond restating where sessionId and operationId come from, so the baseline 3 applies.

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?

States a specific verb (read) and resource (text file) plus scope (approved project, whole or by line range), which cleanly separates it from siblings like fs_list, fs_search, fs_write, and fs_replace. An agent can identify the tool's function 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?

Gives a clear trigger ('when the user wants to read a text file') and prerequisites (sessionId from execution_session_open, a new operationId). It does not explicitly name alternatives such as fs_search or fs_list, nor state exclusions like binary files, so it stops short of full when-not guidance.

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