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

Annotations already declare readOnlyHint, idempotentHint, and destructiveHint, covering the safety profile. The description adds valuable behavioral detail beyond that: it specifies the two calculation speeds (225 wpm silent, 130 wpm read-aloud) and that word count is also returned. This is useful context an agent can rely on when interpreting results.

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 plus a source URL, with no fluff. The main purpose is front-loaded, output details follow, and the source link is a compact addition. Every sentence earns its place, making this a model of concise tool documentation.

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 single-parameter, read-only, idempotent utility with an output schema, the description is complete. It states the purpose, the specific return values, and the calculation assumptions. An agent has everything needed to call it correctly; no missing fields, side effects, or edge-case warnings are likely to matter for this simple 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 coverage is 100% – the only parameter, 'text', is already described as 'The text to measure.' The description adds minimal extra meaning: it clarifies the expected input is a 'block of text' and mentions word count, but this does not significantly enhance schema semantics. 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 opens with a specific verb+resource: 'Estimate how long a block of text takes to read.' This clearly distinguishes the tool from siblings like word_counter or character_counter, though it does not explicitly name an alternative. The resource is unique enough that an agent should not confuse it with other calculator tools.

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?

Usage context is implied by the description – you pass text and get reading time. However, there is no explicit guidance on when to prefer this over similar text tools like hopi_word_counter, nor any exclusions or prerequisites. It is adequate but leaves the when-to-use decision to inference.

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