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

Annotations already declare readOnlyHint, idempotentHint, destructiveHint=false and openWorldHint, so the sentence 'Read-only: returns public data and changes nothing' largely restates structured data. The one genuinely additive fact is 'Costs 1 credit per request', which is useful budget context not available elsewhere. With no output schema, it still says nothing about the shape of the returned calendar/totals, so it does not go far beyond the annotation baseline.

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?

Three short sentences, front-loaded with purpose, then safety, then cost — easy to scan with no filler. Slight deduction because the read-only sentence duplicates annotation content and could have been spent on return-value detail instead.

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 three-parameter read tool with fully documented parameters, the description covers purpose, safety, and cost adequately. Because there is no output schema, the definition leaves the return shape (per-day calendar vs. aggregated totals, fields returned) entirely unexplained, which is the main remaining gap.

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%, with from/to format, inclusivity, defaults, and the one-year window constraint all documented in the schema. The description adds no parameter meaning at all, so the baseline 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 names a specific verb (Fetch) and a specific resource (a GitHub user's contribution calendar and totals), which is meaningfully narrower than the sibling github_get_profile. An agent can tell what this returns without opening the schema, though it never explicitly contrasts itself with github_get_profile.

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 purpose statement — there is no explicit when-to-use, when-not-to-use, or named alternative among the many github_* siblings. The read-only note mildly signals it is a lookup rather than a search, but the agent must infer that a profile lookup belongs to github_get_profile instead.

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