ReadMassiveEstimate

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

With no annotations, the description carries the full burden. It discloses that images are NOT returned, that the tool reports per-model estimates, and includes the cost. It explains the compression_ratio semantics. However, it does not mention error behavior, invalid-path handling, or any limitations, which keeps it just shy of 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?

The description is structured with clear sections and uses a concise, front-loaded summary. The instructions are purposeful and not redundant. It is slightly longer than necessary but every part adds value, justifying a 4 rather than a 5.

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?

Given the simple schema (1 param) and the presence of an output schema, the description covers the tool's purpose, usage, return format, and interpretation well. Minor omissions like error cases and concrete examples prevent a 5, but the description is complete enough for an agent to invoke the 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?

The schema provides only a name and type for 'paths' (string or array). The description adds 'A single file path or a list of file paths,' which clarifies the semantic meaning slightly but does not specify path formats, file type restrictions, or how paths relate to the estimation output. For a single trivial parameter, this is adequate but not rich.

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 explicitly states the tool's function: 'Report text-vs-image token counts, compression ratio, and dollar cost per model — WITHOUT returning the images.' The verb 'Report' and the resource (token counts/cost) are specific, and it clearly distinguishes itself from ReadMassive by noting it avoids returning pixels.

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 description provides explicit when-to-use guidance: 'USE THIS FIRST to decide whether reading a file as a packed image is worth it, before spending context on the pixels via ReadMassive.' It also gives a clear exclusion: if compression_ratio < 1, 'just read the file normally.' This names the alternative tool and the decision rule.

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