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

readOnlyHint already establishes the safe-read profile, so the bar is lower. The description adds genuine behavioral value by enumerating issue categories (structure, security) and the shape of each returned issue (stable arch.* code, severity, English message, actionable suggestion) — useful detail given there is no output schema.

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?

Purpose is front-loaded, followed by category detail, issue shape, and usage — a logical order with no filler. It is dense but every clause contributes, though the category enumeration is slightly long for the value it adds.

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?

With no output schema, the description compensates by describing the returned issue structure and severity vocabulary, and it covers both usage triggers and validation scope. An agent has enough to call and interpret this correctly; only explicit sibling routing is missing.

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% and both parameters (severityFilter enum, expectedProjectId) are thoroughly documented in the schema itself. The description adds nothing about parameters, so the 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?

States a specific verb and resource: 'Runs the validation engine on the current architecture diagram and returns the list of issues.' The 'architecture diagram' scope distinguishes it from siblings like validate_process_flow, validate_journey and validate_captable without needing their schemas.

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?

Explicitly gives when-to-use: 'Fits before presenting the architecture to the user, or when they ask check my architecture.' That is clear context, but it does not explicitly exclude the adjacent validate_* siblings or state prerequisites, so it falls short of a 5.

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