project_facts

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

Annotations already indicate readOnlyHint and idempotentHint. The description adds behavioral context by characterizing the tool as a 'reef read tool' and the facts as 'durable' and the 'calculated substrate behind findings.' No contradiction with annotations.

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 purpose, no redundant words. Every sentence adds value.

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?

Despite an output schema existing, the input schema lacks descriptions and the description covers only half the parameters. Important context about project identification, freshness, and limits is missing. The description is insufficient for an 8-parameter tool with 0% schema coverage.

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 0% (no descriptions). The description lists only 4 out of 8 parameters (overlay, source, kind, subjectFingerprint), providing meaning for those but omitting projectId, projectRef, freshnessPolicy, and limit. This leaves critical parameters undocumented.

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 identifies the tool as a read operation for 'durable project facts' and lists the query dimensions (overlay, source, kind, subject fingerprint). It distinguishes itself from sibling tools by emphasizing that it returns 'calculated substrate behind findings without rerunning analysis.'

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 states when to use the tool: 'when an agent or shell needs the calculated substrate behind findings without rerunning analysis.' It does not list alternative tools by name, but the context is clear enough to guide selection among siblings.

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