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

With no annotations, the description carries the full burden. It discloses the read-only nature ('Read'), explains the projection over events, and details the merging behavior for work/project pass-throughs. It does not mention side effects (expected none for a read) or access-control requirements, but the disclosed behavior is sufficient for safe invocation.

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, each earning its place. The core purpose is front-loaded in the first sentence, and the parameter guidance is compact and direct. No fluff or repetition.

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 read tool with an output schema, the description covers the operation, the parameters, and the key merging behavior. It does not mention pagination or limits, but these are unlikely to be critical for a spine read and are partially covered by the output schema signal. Adequate for the tool's complexity.

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 100%, so baseline is 3. The description adds meaningful value beyond the schema: it clarifies that exactly one ID should be passed ('Pass one of'), and it explains that work_id and project_id fold evidence from linked runs, which interprets their otherwise generic schema descriptions. This exceeds baseline.

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 opens with a precise verb and resource: 'Read the case-file spine' and lists the states it covers (required/received/missing/superseded). This clearly distinguishes it from write-type siblings like evidence_attach and event-listing tools like event_list, so an agent can tell it apart without opening the schema.

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 gives explicit parameter usage ('Pass one of run_id, work_id, or project_id') but does not state when to prefer this over alternatives, nor does it give negative guidance like 'use evidence_attach to add evidence' or 'use event_list for raw events'. The purpose implies when to use it, but explicit routeing is missing.

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