byte_count

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

With no annotations, the description must carry the burden. It discloses the encodings and utility but does not mention edge cases, output format, or limitations (e.g., invalid UTF-8 handling). The PRO trial note is present but doesn't add behavioral insight.

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?

Two sentences, front-loaded with the core purpose, and no redundant wording. The trial-use prefix is minor but doesn't undermine overall conciseness.

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 simple one-parameter tool, the description covers purpose and use cases well. However, without an output schema, it doesn't state how results are returned (e.g., single number vs. per-encoding object), which is a slight gap.

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 input schema already fully documents the single parameter with 'Text to measure' (100% coverage). The description adds no additional parameter-specific detail, so baseline 3 is appropriate.

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 clearly states the tool counts byte length of a string and enumerates three encodings (UTF-8, UTF-16, ASCII). This specific verb+resource distinguishes it from sibling tools like word_count and char_info.

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 provides concrete use cases: 'checking API payload sizes and database field limits.' While it doesn't explicitly compare against sibling tools, the context is clear and actionable.

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