The question/claim: "Is making a vow at a tomb, tying a cloth to the railing, asking a saint for healing/children/work a religious act of worship? Or is it superstition?"
What does the Qur'an say? — supplication and worship are for God alone
"The mosques are for God, so do not invoke anyone alongside God." (72:18)
"You alone we worship, and You alone we ask for help." (1:5)
"And when I am ill, it is He who heals me." (26:80)
Drawing the line (multi-vocal)
- Visiting graves is lawful and Sunnah. The Prophet said, "Visit graves, for they remind you of the Hereafter" (Muslim, Funerals). There is no dispute here.
- Asking the dead / a saint (for healing, children, work): the large majority of scholars (the Salafī line + many Sunnīs) hold this contrary to monotheism, since by 72:18 and 1:5 supplication/help is from God alone.
- Tawassul (using a means): asking God "by the standing of" the deceased is a contested matter: some scholars (parts of the Sufi/Sunnī tradition) permit it, others (the Ibn Taymiyya line) forbid it. This is different from asking the dead directly.
- Tying cloths, lighting candles, seeking help from tomb stones: these have no place in the Qur'an or Sunnah; they are folk belief/superstition.
An honest limit
- Religious: visiting the grave and supplicating to God for the deceased.
- Contested: tawassul by the standing of a saint.
- Cultural/superstition: vowing to a tomb, tying cloths, seeking healing/children directly from the tomb.
Conclusion: visiting a grave and praying to God for the deceased is religious; but vowing to a tomb and tying cloths are not in the Qur'an — they are a cultural practice, and become problematic for monotheism once they turn into "asking the dead." As for the permissible form of tawassul, we do not reduce it to one view; we note it is contested.
Source: Qur'anic verses (M. Okuyan meal) + authentic Sunnah (grave-visiting: Muslim, Funerals). Views are given by name and multi-vocally; not a fiqh fatwa.