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

Annotations already declare readOnlyHint, idempotentHint, destructiveHint=false and openWorldHint=false, so the safety profile is covered. The description adds genuinely new behavioral context: the response may contain end-user personal data, with instructions to quote minimally and mask direct identifiers — a handling constraint found nowhere in the structured fields.

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, zero waste: the action comes first and the PII-handling constraint follows immediately. Every clause earns its place.

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?

An output schema exists, so return shape needn't be described, and annotations cover the safety profile; the PII caveat closes the biggest remaining risk for a tool returning end-user data. The gap is that the meaning of "evidence" and how the three optional scoping parameters change the result set are left entirely to the schema.

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 86%, so the schema already explains range, user_id, agent_name, reason and user_intent. The description adds nothing about how user_id/agent_name/range scope the returned evidence, which is the one place prose could have exceeded the schema. Baseline 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?

Specific verb + resource: "Get one Flowlines signal and its evidence." The singular "one ... signal" implicitly distinguishes it from the sibling list_signals, but the description never names that alternative, so the differentiation is only inferable.

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 implied by the singular-resource phrasing (fetch details for a known signal_id), but there is no explicit when-to-use / when-not statement and no pointer to list_signals for discovery or to get_session/get_turn for adjacent evidence. A required reason/user_intent pair in the schema suggests a reasoning-audit model, which the description never explains.

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