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

Annotations already declare readOnlyHint=true, so the safety profile is covered in structured data. The description adds real context beyond that — it discloses the returned fields (including missing glyphs for a supplied sample and a specimen URL) and states 'Free', implying no cost or licensing side effect. It says nothing about failure behavior for unknown font ids or whether the specimen URL is stable.

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 short fragments, front-loaded with the resource and its returned contents, with no filler. The telegraphic style borders on under-specification but every clause carries information.

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?

With no output schema, the description serves as the return-value contract by listing the sections an agent will get back, which is the key thing needed for a read-only preview tool with full schema coverage. Only minor gaps remain, such as error behavior for an invalid font_id.

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% and the description only restates the sample parameter's purpose ('missing glyphs for a sample text'), which the schema already conveys as 'Text to check glyph coverage for'. Baseline 3 is appropriate when the schema carries the parameter documentation.

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 names the resource ('one font') and enumerates the payload it returns: styles, scripts, metrics, glyph coverage, specimen URL. That is enough to distinguish it from the sibling set (search_fonts for discovery, get_family for a family-level view), though it never uses a verb so the 'retrieve' framing is inferred rather than stated.

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 implied rather than stated: the font_id example in the schema is 'from search_fonts', which suggests this is a drill-down after search. The word 'Free' is a useful cost signal against quote_license/buy_license, but there is no explicit when-to-use or when-not-to-use statement, and no alternative is named.

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