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

Annotations already declare readOnlyHint=true, and the description confirms 'Read-only; returns no credentials', adding a security-relevant detail. It also discloses behavior for edge cases: days with no data are marked no_data (unknown, never zero or healthy) and insufficient measurements yield not-enough-data rather than a guess. These go beyond the annotations and are valuable for interpreting results.

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 that front-loads the main purpose (one project's last 30 days) and then enumerates specific metrics and the verdict. It is efficient, with every clause adding relevant detail, and does not include fluff or redundancy. It is slightly long but appropriately so for the complexity.

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?

Given there is no output schema, the description explains the output semantics well: it describes the verdict comparison, the handling of no_data and not-enough-data, and the read-only nature. It covers the key behaviors an agent needs to know to interpret results correctly. It does not specify the exact response structure or field names, but for a trend report tool this 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?

Schema description coverage is 100%, meaning the schema already fully documents install_id and read_token. The description does not add any new parameter information beyond what the schema provides; it only refers to 'same card' which is already in the schema descriptions. Therefore, the description adds no semantic value for parameters, and the baseline of 3 is appropriate.

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 the tool's function: it analyzes one project's last 30 days of measurements, including metrics like screen time, poor ratings, crashes, and alerts, plus a 7-day verdict. It specifies the resource (one project) and the time range, distinguishing it from sibling tools that likely cover other aspects (e.g., crash_risk, alerts, session_summary). The verb 'trend' is implicit but the resource and scope are explicit.

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 provides context about what the tool does but does not explicitly state when to use it versus alternatives. There is no mention of 'use this when you need a trend report' or exclusions like 'use boosthis_session_summary for daily detail'. Usage is implied by the description but not directly guided, leaving the agent to infer.

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