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

Annotations already declare readOnlyHint=true, destructiveHint=false and openWorldHint=true, so the safety profile is covered by structured data. The description adds one genuinely non-obvious behavioral fact — that each call costs 1 credit — but says nothing about truncation on very long inputs or how non-word tokens are counted. With annotations doing most of the work, a 3 is appropriate.

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 content is short, but the title is redundantly restated at the start ('Reading Time Calculator: Reading Time Calculator estimates...'), wasting the most prominent position on a duplicate rather than front-loading the actual capability. The credit-cost note is useful but appended as a parenthetical rather than integrated.

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 two-parameter, read-only calculator with full schema coverage, an output schema, and complete annotations, the description covers the essentials. It only falls short on edge-case behavior such as input length limits or how the WPM default is applied.

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 both 'text' and 'wpm' are already documented in the schema, including the 250 WPM default. The description only echoes that reading speed is customizable, adding no format, range, or behavior detail (e.g. what happens with an out-of-range wpm) beyond the 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?

The description states a specific verb and output ('estimates how long it will take to read a given text') and names the underlying mechanism (word count plus WPM). An agent can tell this apart from nearby tools like TextReadabilityScore or SyllableCounter by the explicit 'reading time' framing, though it never names an alternative directly.

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?

There is no guidance on when to choose this over TextReadabilityScore, WordLexiconAnalyzer, or SyllableCounter, and no stated preconditions such as text length limits. The only contextual note is the credit cost, which is billing rather than usage guidance.

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