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

Annotations already declare readOnlyHint, idempotentHint, and destructiveHint=false, yet the description still adds substantial behavioral context: it enumerates exactly which fact categories come back (rooms, doors, windows, circulation, zones, storeys, bbox, freedom, totals) and clarifies derived vs. hand-authored data. Details like floor_circle area being exactly πR² and levels[i] carrying per-floor facts go well beyond what structured fields provide.

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 purpose is front-loaded in the first clause, before the long enumeration of returned facts. The single sprawling second sentence is dense and would read better as a list, but every element it names carries information an agent needs to interpret the response.

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 carries the burden of explaining return values and does so comprehensively — covering geometry keys, per-storey structure, reachability, bounding extents, and totals. An agent knows what to expect from the result without additional documentation.

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?

There is a single required parameter, `source`, and schema description coverage is 100%, so the schema already documents it ('ArchLang source.'). The description adds nothing about the source format, dialect, or constraints, so it only meets the baseline for a fully-covered schema.

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 — 'Report a plan's facts without rendering' — and draws a clear line between fact extraction and image rendering. It does not, however, explicitly differentiate itself from sibling inspection tools like lint, validate, or score, so the agent must infer that this one is purely descriptive.

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 phrase 'so you can check it against the brief without looking at an image' implies a usage context (verifying facts rather than viewing geometry), but there is no explicit when-to-use/when-not-to-use statement and no named alternative among lint/validate/score/compile.

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