get_axis_registry

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

Annotations already declare readOnlyHint=true, and the description adds behavior beyond that: it reveals the return contents and the optional-filter semantics of the tag parameter. No contradiction with annotations.

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 sentences with no fluff: the resource and its contents are front-loaded, and the parameter behavior is stated in one imperative sentence. 'And the rest' is a minor fuzziness but does not waste words.

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 one-optional-parameter lookup tool with a readOnly annotation, the description covers the resource contents and filtering behavior. It does not explicitly state what happens when tag is omitted, but the phrasing implies a full registry return, which is sufficient.

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?

With 0% schema description coverage, the description carries the param burden. It explains that 'tag' selects a single entry and gives concrete valid examples (wght, wdth, opsz, slnt, ital, GRAD), adding real meaning over the bare 'string' 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?

States a specific resource (variable-font axis registry) and its contents (name, description, min, max, default per axis tag). The example tags distinguish it clearly from sibling font-search/font-download tools.

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: call this when you need axis-tag metadata, and pass a tag to narrow to one entry. But it never explicitly contrasts with siblings like get_font or search_fonts, nor states when not to use it.

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