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

Annotations already declare readOnlyHint=true, idempotentHint=true, destructiveHint=false, and openWorldHint=true, so the description's trailing 'Read-only.' simply restates structured data and earns no credit. It adds no behavior context beyond annotations, such as the time window the metrics cover, whether historical data is required, or whether missing developers error or return empty.

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, front-loaded with the metric list and followed by the routing cue; nothing is padded or repeated. The only redundancy is the one-word 'Read-only.' which duplicates the annotation, but it costs almost nothing.

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 one-parameter read tool with no output schema and rich annotations, the description covers purpose and use case adequately, and the enumerated metrics tell the agent what to expect back. The notable gap is that no time window or aggregation period for the metrics is specified anywhere, which matters when interpreting throughput or cycle time.

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 a single parameter at 100% schema description coverage, the schema fully documents 'login' as a GitHub username with an example. The description adds no extra meaning, such as how ambiguous or renamed logins are resolved, 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?

States a specific verb and resource ('Get metrics for an individual developer') and enumerates the concrete metrics returned: PR throughput, review activity, average cycle time, code contributions. The word 'individual' implicitly separates it from team/org-level siblings like get_team or get_org_health, though no sibling is named explicitly.

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?

'Use this when asked about a specific engineer's activity or productivity' gives a clear triggering condition tied to a single developer, which is enough to route an agent away from team-scoped tools. It stops short of naming alternatives explicitly or stating when not to use it (e.g., when the target is a whole team or repo).

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