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

Annotations already declare readOnly, idempotent, non-destructive and closed-world, so the safety profile is covered. The description adds value beyond that: a hard 48 KB content cap, a refusal of binary and symlink targets, and the authorization model (account-bound computer:write OAuth plus a prompted local owner approval). Those are exactly the non-obvious behavioral facts an agent needs before calling.

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 dense sentences with zero filler. The core capability and its bounds come first, and the sibling routing plus auth requirements follow in a logical order.

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 two-parameter read tool with full schema coverage and no output schema, this covers scope, limits, exclusions, auth and the sibling alternative. The only omission is what the response actually contains (raw text vs. encoded/truncated content when near the 48 KB edge), which is a minor gap rather than a blocking one.

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%: 'area' already documents the allowed managed-home values with no arbitrary roots, and 'path' already documents scope and the no-symlink-traversal rule. The description restates the same constraints ('managed-home', no symlink traversal) without adding syntax, path-format examples, or relative-vs-absolute guidance. Baseline 3 is appropriate when the schema does the heavy lifting.

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 ('Read one managed-home text file'), then immediately bounds it with size (48 KB) and exclusions ('not binaries or symlinks'). The final clause contrasts it with exza_read_home_text_files, so an agent can pick the right tool without opening either 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?

Explicitly routes multi-file cases to exza_read_home_text_files with a concrete range (1-8 related files) and a stated rationale (single bounded request). It also excludes binaries and symlinks from this tool's scope. The one gap is that it never says how to discover a valid path in the first place (siblings like exza_list_home_files or exza_search_home_files).

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