get_dir_size

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

The annotations already declare this a safe read (readOnlyHint=true, destructiveHint=false), so the bar is lower. The description adds genuine behavioral content beyond that: recursion into all subdirectories and the three metrics returned. It omits any warning about cost/latency on very large trees or permission-denied behavior, so it is not a 5.

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, zero waste, with the core action front-loaded and the usage hint deferred to the end where it belongs.

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 an output schema present, the description need not explain the return payload, and the annotations cover safety. It is nearly complete for a single-parameter read tool; the remaining gap is the absence of any caveat about slow scans on large directories.

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 0%, but there is only one parameter and the description implicitly constrains it to a directory rather than a file. It says nothing about absolute vs relative paths or symlink handling, so it adds only marginal meaning over the bare 'path: string' 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?

States a specific verb and resource ('Calculate the total size of a directory') with the recursive scope made explicit ('including all files and subdirectories'). It is plainly distinguishable from siblings like get_file_info and list_files, which do not aggregate sizes.

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?

'This is the best tool for answering how much space does X use questions' gives a clear usage context and implicitly routes the agent away from list_files/get_file_info. It does not name an alternative tool or state when not to use it, so it stops short of a 5.

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