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

There are no annotations, so the description carries the burden. It does disclose that the tool returns titles, one-line summaries, and URLs)SkipL, which signals a read-only index behavior. But it does not explain what the lang parameter does, whether ja changes the content language, or any other behavioral caveats.

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?

One compact sentence front-loads the resource and purpose, uses a list to convey scope, and ends with the precise return format. Every phrase contributes useful 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?

For a simple one-parameter index tool, the description covers purpose, content, and return shape. The main gap is the unexplained lang parameter, but the default and enum values make the tool usable without further detail.

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%, yet the single parameter is an optional enum with 'en', 'ja', and a default of 'en', so the schema largely documents itself. The description does not add any meaning to the lang parameter, which would have been helpful.

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 states a clear resource ('Index of the English field guide for engineers using GNSS in Japan') and lists concrete topics plus the return payload (titles, one-line summaries, URLs). It is specific enough to distinguish itself from tools like rtk_bases_near, though it does not explicitly contrast itself with any sibling.

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 context is implied by the topic list and the word 'Index' – an agent can infer that this is for retrieving guide entries rather than, say, nearby base stations. However, there is no explicit when-to-use guidance or mention of alternatives such as rtk_bases_near.

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