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

Annotations only say non-readOnly and non-destructive; the description adds the real behavior: the reply returns 'stopping' immediately but completion takes a minute or two, confirmed via fastero_get_streamlit_app, files and settings survive, and a deleted or out-of-project app returns 'Streamlit app not found.' It also discloses the permission model (owners, admins, editors).

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 core action and its non-destructive nature are front-loaded in the first sentence, and every subsequent sentence maps to a real decision (verify, don't bother for idle apps, restart path, delete path, permissions). It runs long, and the idle-timeout/organisation-setting clause could be tightened, but no sentence is pure 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 mutation with no output schema, the description covers timing, verification route, reversibility, error behavior, permissions and the sibling alternatives. Nothing an agent needs to decide whether and how to call it 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?

Both parameters are fully documented in the schema at 100% coverage (appId from fastero_list_streamlit_apps, projectId from fastero_list_projects), so the baseline of 3 applies. The description adds only indirect meaning via the 'not in this project' error case and does not restate or enrich parameter formats.

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 ('Stop a Streamlit app's server') plus the crucial scope qualifier that files and settings are preserved. It also explicitly says what it is not: not a delete (that is fastero_delete_streamlit_app) and not something an idle app needs. An agent can separate it from every nearby sibling without opening a 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?

Gives explicit when-to-use and when-not-to-use guidance: idle apps need no stopping because they sleep on their own idle timeout, unless always-on, in which case fastero_set_streamlit_always_on is the lever. It names the alternatives for restart (fastero_run_streamlit_app / member opening the link), for removal (fastero_delete_streamlit_app) and for verification (fastero_get_streamlit_app).

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