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

Annotations already declare readOnlyHint=true and openWorldHint=false, so the safety profile is covered; the description adds real behavioral context beyond that — images return as the picture itself rather than text, and video/audio are unsupported. It omits any truncation behavior tied to max_chars, but the added format-handling detail is meaningful.

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?

One dense sentence, front-loaded with the core action, then the accepted inputs, then the format support and the image/video exclusions. Every clause carries information; nothing is filler.

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 no output schema, the description covers the source of url, supported formats, image return behavior, and unsupported media. What's missing is minor — nothing about what happens to very large files or error behavior when a URL is invalid — but an agent has enough to call it correctly.

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 only 50%: max_chars is documented ('Default 20000, max 100000') but url has no schema description. The description compensates by explaining what url should contain (a URL from list_record_files, a record, or an email attachment), which is the key semantic an agent needs. It adds little on max_chars since the schema already covers it.

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 (read) and resource (file text in this workspace), enumerates the accepted source forms (URL from list_record_files, a record, or an email attachment) and the supported formats, and explicitly carves out video/audio. An agent can distinguish it from siblings like view_images or read_email_thread immediately.

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?

Names the alternative for bulk images ('view_images does up to 10 at once') and states the exclusions (video and audio aren't read), which routes the agent correctly for image-heavy cases. It does not cover other potential alternatives (e.g. read_email_thread for threads, list_record_files for discovery), so it stops short of full when/when-not guidance.

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