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

No annotations are provided, so the description carries the full behavioral burden. It helpfully discloses cost ($0.003/call, USDC on Base), but says nothing about output format, handling of malformed input, or limits, leaving the mutation/read profile and return structure unstated.

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?

A single front-loaded sentence naming the core function first and appending the cost detail. Nothing is wasted, though the parenthetical pricing slightly dilutes the core purpose statement.

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 trivial one-parameter counting utility with no annotations or output schema, the description covers the essential purpose and metrics. It stops short of explaining what the response contains (individual counts per unit) and any behavioral constraints, which would matter for autonomous invocation.

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?

There is a single parameter ("text") with 0% schema description coverage, so the description must compensate. The phrasing implies the input is the string to measure, which is nearly self-evident for a counting tool, but the parameter name is never explicitly tied to its meaning or format.

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 clear verb ("Count") and a specific resource ("user-perceived characters (graphemes)"), and even clarifies the multiple metrics produced (vs. code points, UTF-16 units, bytes). It is distinguishable from near siblings like tk_unicodeNormalize and tk_detectEncoding, though it never names them explicitly.

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 gives no guidance on when to reach for this tool versus alternatives such as tk_detectEncoding or tk_scriptDetect, nor any prerequisites. The only ancillary info is pricing, which is not usage guidance.

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