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

readOnlyHint=true already establishes the safe read-only profile, so the description is not the sole carrier of behavioral information. It adds which metrics are computed, but says nothing about scope of counting (e.g. whether it covers the whole package or only the body), performance, or result shape.

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 with no filler; every listed item is informative and nothing is redundant.

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 read-only counting tool with 100% schema coverage and an annotation confirming read-only behavior, the description is sufficient; the enumeration of counted items effectively signals what comes back even without an output schema. Only the counting scope is left unstated.

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 the 'doc' path and the 'stories' enum semantics are fully documented in the schema itself. The description contributes no additional parameter meaning, which is the expected baseline when the schema does the heavy lifting.

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 ('Counts') plus an explicit enumeration of the resources counted (paragraphs, words, headings, tables, comments, revisions, fonts, styles). An agent can distinguish it from list-style siblings like paragraphs_list or revisions_list, though it does not explicitly contrast with the nearby 'info' tool.

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 is only implied by the enumeration: an agent infers it is the tool for aggregate document metrics. There is no explicit when-to-use statement, no exclusions, and no pointer to alternatives such as info or page_estimate.

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