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

Annotations already declare readOnlyHint=true and openWorldHint=false. The description adds valuable behavioral context: 'keyless' indicates no auth needed, 'daily' indicates update frequency, and it discloses return fields (momentum_score, breakout_share, language_mix, and the 8 hottest new repos). This goes beyond the annotation safety profile.

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?

The description is a single dense sentence covering methodology, outputs, and auth, followed by a usage sentence and update cadence. No wasted words, though the first sentence is slightly packed and could be split for readability.

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?

The tool is simple (one optional param, no output schema, read-only annotation), and the description covers purpose, use cases, return fields, update frequency, and authentication. The schema handles the `days` parameter, so no critical aspects are missing.

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% for the single optional parameter `days`, which includes a full description and Gold tier requirement. The tool description doesn't mention the parameter, but the schema carries the burden, so the baseline score of 3 applies.

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 clearly states 'Returns a 0-100 open-source creation momentum index' and explains the specific criteria (new GitHub repos from the last 30 days with >10 stars, baseline, breakout tilt). It distinguishes this tool from generic GitHub trend tools by defining its unique methodology and output fields.

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?

The description explicitly provides usage contexts: 'Call when the user asks about open-source momentum, GitHub trends, hot new repos, or language shifts, or when timing devtools launches, DevRel spend, or OSS deal sourcing.' It gives clear when-to-use guidance, though it doesn't name alternatives or exclusions.

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