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

Annotations already declare readOnlyHint=true and openWorldHint=false, so safety is covered; the description adds genuinely new behavioral facts — that execution is pure computation with no cost or external dependency. It stops short of stating determinism, size limits, or how the token estimate is derived beyond the ~4 chars/token heuristic.

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 compact clauses, front-loaded with the operation and its outputs, with the operational note trailing. No filler, nothing repeated from the schema or annotations.

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 one-parameter utility with no output schema, the description enumerates the returned metrics (chars, words, lines, tokens) plus the token heuristic, which is nearly all an agent needs. Only the exact result shape and edge-case behavior remain unstated, which is minor here.

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 0%, but the single required parameter is named "text" and the description says counts are computed "of a text," so its meaning is effectively conveyed. No detail is added on accepted encoding, empty input, or whether whitespace-only lines count, so it does not fully compensate for the coverage gap.

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 specific verb (count/estimate) and enumerated outputs (characters, words, lines, tokens) for a clearly scoped resource: a text input. It is trivially distinguishable from siblings like bursia_levenshtein, bursia_slugify, or bursia_case_convert, which transform or compare text rather than measure it.

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?

"Pure computation, free" signals the operational context (no network, no billing, no side effects), which helps an agent decide to call it casually. However, it never states when to prefer this over alternatives or any exclusions/edge cases (empty string, unicode, large inputs), so usage is only implied.

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