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

Annotations only declare it a safe read; the description adds substantial context beyond that: live status is verified against the app's server, files are truncated past 50,000 chars each / 300,000 total and flagged with truncatedFrom, viewerUrl is member-only, a missing/deleted app returns "Streamlit app not found.", and any project member including viewers may call it.

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?

Front-loaded with the core verb and resource, and every sentence carries information — field inventory, use cases, alternatives, truncation limits, sharing, not-found behavior, permissions. It is a single dense block rather than clearly segmented, which costs a point but nothing is redundant.

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?

There is no output schema, so the field enumeration is load-bearing and thorough. Combined with truncation limits, permission scope, error behavior and sibling routing, an agent has everything needed to call this and interpret the result 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 100% and both parameters already document their provenance (appId from list_streamlit_apps, projectId from list_projects), so the baseline is 3. The description names appId in the field list but adds no format, syntax or constraint detail beyond what the schema provides.

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?

"Read one Streamlit app with its files" gives a specific verb, resource and scope, then enumerates the exact returned fields (status, alwaysOn, errorMessage, source, viewerUrl, per-file path/name/content). It explicitly separates itself from fastero_list_streamlit_apps (no files) and fastero_get_streamlit_app_logs (start-up output), so an agent can pick correctly without opening 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?

Two concrete use cases are stated: reading an app's code before changing it, and checking whether a start has finished. The alternatives are named with the condition that selects each — list_streamlit_apps for metadata only, get_streamlit_app_logs for startup/pip errors — and sharing is redirected to fastero_invite_to_project since there is no public link.

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